Below and attached are two huge approximations of the MRB constant using only integers and the form Sum[x^(-n!), {n, 2, Infinity}],, for x from 2 to 101..
This first one gives around 3000 accurate decimals.
And the one below it gives around 4000 accurate decimals!
In[7]:= TranscendentalRecognize[num_?NumericQ, basis_?VectorQ] := 
 Module[{lr, ans}, 
  lr = FindIntegerNullVector[Prepend[N[basis, Precision[num]], num]];
  ans = Rest[lr].basis/First[lr];
  Sign[N[ans]] Sign[num] ans]
m = NSum[(-1)^n*(n^(1/n) - 1), {n, 1, Infinity}, 
   Method -> "AlternatingSigns", WorkingPrecision -> 4000]; 
s = Table[Sum[x^-(n!), {n, 2, Infinity}], {x, 2, 102}]
In[50]:= TranscendentalRecognize[N[m, 3000], s[[2 ;; 101]]]
Null
N[m - (-1617601210758780475076147232954091*
      Sum[3^(-n!), {n, 2, Infinity}] + 
     1260730972958628376379103266584756*
      Sum[4^(-n!), {n, 2, Infinity}] + 
     168255942381333226880232447282467*
      Sum[5^(-n!), {n, 2, Infinity}] + 
     526758508745229051826843765249190*
      Sum[6^(-n!), {n, 2, Infinity}] - 
     2670042164293488356909920338891358*
      Sum[7^(-n!), {n, 2, Infinity}] + 
     3829272605182291498586693806942722*
      Sum[8^(-n!), {n, 2, Infinity}] + 
     859415018288984049908165889504129*
      Sum[9^(-n!), {n, 2, Infinity}] + 
     3980672361148310552936792479918956*
      Sum[10^(-n!), {n, 2, Infinity}] + 
     2949125963814399232221423020582609*
      Sum[11^(-n!), {n, 2, Infinity}] - 
     1704497602955159964193025017671421*
      Sum[12^(-n!), {n, 2, Infinity}] - 
     1158615646978266430347663044541968*
      Sum[13^(-n!), {n, 2, Infinity}] + 
     2940566178482760393686097895245937*
      Sum[14^(-n!), {n, 2, Infinity}] + 
     3537625077232750001025112741131143*
      Sum[15^(-n!), {n, 2, Infinity}] + 
     1628630162143702095790590207317237*
      Sum[16^(-n!), {n, 2, Infinity}] + 
     2075441527976471396863264573730348*
      Sum[17^(-n!), {n, 2, Infinity}] - 
     2264173752934939591163612937875735*
      Sum[18^(-n!), {n, 2, Infinity}] - 
     2522296388129947914734380874599382*
      Sum[19^(-n!), {n, 2, Infinity}] + 
     2320118429832380290630535582086539*
      Sum[20^(-n!), {n, 2, Infinity}] - 
     2463815400152015299479476128150570*
      Sum[21^(-n!), {n, 2, Infinity}] + 
     2638986590182329976236035098810060*
      Sum[22^(-n!), {n, 2, Infinity}] + 
     3251654159711357468899799174679152*
      Sum[23^(-n!), {n, 2, Infinity}] + 
     93915231319017548602476626871287*
      Sum[24^(-n!), {n, 2, Infinity}] + 
     193808727512029207895977355455647*
      Sum[25^(-n!), {n, 2, Infinity}] + 
     3607117201144790057874151852014759*
      Sum[26^(-n!), {n, 2, Infinity}] + 
     3262007418561507649847272272032955*
      Sum[27^(-n!), {n, 2, Infinity}] + 
     2480402689383408099208714687051739*
      Sum[28^(-n!), {n, 2, Infinity}] + 
     1308509867990398861324717427268301*
      Sum[29^(-n!), {n, 2, Infinity}] + 
     1311639103727367378793170201050131*
      Sum[30^(-n!), {n, 2, Infinity}] - 
     1648727214133032285519999314329705*
      Sum[31^(-n!), {n, 2, Infinity}] + 
     3895395322625799512405275036584486*
      Sum[32^(-n!), {n, 2, Infinity}] - 
     4228124835647564954643945470573976*
      Sum[33^(-n!), {n, 2, Infinity}] + 
     1724355876667841445871244995563479*
      Sum[34^(-n!), {n, 2, Infinity}] - 
     821120993451512960591013772378796*
      Sum[35^(-n!), {n, 2, Infinity}] - 
     2219010432574623362013336951784027*
      Sum[36^(-n!), {n, 2, Infinity}] + 
     955107235645995663705816457381081*
      Sum[37^(-n!), {n, 2, Infinity}] + 
     4977626512233618799592076868098467*
      Sum[38^(-n!), {n, 2, Infinity}] + 
     479750350430292719426344888964982*
      Sum[39^(-n!), {n, 2, Infinity}] - 
     1009428065023075859234682582260676*
      Sum[40^(-n!), {n, 2, Infinity}] - 
     453768351398454243808381569101699*
      Sum[41^(-n!), {n, 2, Infinity}] - 
     804331952205012340117978795714571*
      Sum[42^(-n!), {n, 2, Infinity}] + 
     2112537773325380956038299597223034*
      Sum[43^(-n!), {n, 2, Infinity}] + 
     1563909600882194431077161802113231*
      Sum[44^(-n!), {n, 2, Infinity}] + 
     3281512201875089338818140791672361*
      Sum[45^(-n!), {n, 2, Infinity}] - 
     841693145563449440980152624889040*
      Sum[46^(-n!), {n, 2, Infinity}] - 
     1180596415104015890930529257781618*
      Sum[47^(-n!), {n, 2, Infinity}] + 
     256894002482080676102804595099554*
      Sum[48^(-n!), {n, 2, Infinity}] + 
     3059743069488164456875317821197684*
      Sum[49^(-n!), {n, 2, Infinity}] + 
     618378447020184993694643494855854*
      Sum[50^(-n!), {n, 2, Infinity}] + 
     1207849584860413404886567472602012*
      Sum[51^(-n!), {n, 2, Infinity}] + 
     3269594033521468442241723242546780*
      Sum[52^(-n!), {n, 2, Infinity}] - 
     519110770734317313929892528340481*
      Sum[53^(-n!), {n, 2, Infinity}] + 
     5337933979867080683965490693782692*
      Sum[54^(-n!), {n, 2, Infinity}] - 
     845305587078512215850327456666298*
      Sum[55^(-n!), {n, 2, Infinity}] + 
     3638411700443380962703568627301563*
      Sum[56^(-n!), {n, 2, Infinity}] + 
     57104890901297559220617943398070*
      Sum[57^(-n!), {n, 2, Infinity}] - 
     349193535926582284655062345576058*
      Sum[58^(-n!), {n, 2, Infinity}] - 
     2574102460519834845887788602861507*
      Sum[59^(-n!), {n, 2, Infinity}] + 
     626918354620070457316744226035168*
      Sum[60^(-n!), {n, 2, Infinity}] + 
     925910782814132818900483793749726*
      Sum[61^(-n!), {n, 2, Infinity}] + 
     2659043142343524075790297170462132*
      Sum[62^(-n!), {n, 2, Infinity}] - 
     3776624195115615476424023462853132*
      Sum[63^(-n!), {n, 2, Infinity}] + 
     289252819950910792633107902104858*
      Sum[64^(-n!), {n, 2, Infinity}] - 
     4335832676811110969381326369850434*
      Sum[65^(-n!), {n, 2, Infinity}] - 
     1049666000572944258193455109018929*
      Sum[66^(-n!), {n, 2, Infinity}] - 
     2060181142655155567883399336847960*
      Sum[67^(-n!), {n, 2, Infinity}] - 
     1802686787596758226171368511609941*
      Sum[68^(-n!), {n, 2, Infinity}] + 
     560149266456680122048780702178403*
      Sum[69^(-n!), {n, 2, Infinity}] + 
     45326892699113686458133865345872*
      Sum[70^(-n!), {n, 2, Infinity}] - 
     2189834207054837650558549556270607*
      Sum[71^(-n!), {n, 2, Infinity}] - 
     200007960908326787314318800286238*
      Sum[72^(-n!), {n, 2, Infinity}] + 
     1906908709896907749806302689843055*
      Sum[73^(-n!), {n, 2, Infinity}] - 
     2413831603161356405527598276237701*
      Sum[74^(-n!), {n, 2, Infinity}] + 
     349851432963186321571769787692286*
      Sum[75^(-n!), {n, 2, Infinity}] - 
     1409077148223763233830923073076654*
      Sum[76^(-n!), {n, 2, Infinity}] - 
     3258926296143830773420165267895655*
      Sum[77^(-n!), {n, 2, Infinity}] - 
     2788017156113146729276123053829960*
      Sum[78^(-n!), {n, 2, Infinity}] + 
     2692847787140868892915206384398765*
      Sum[79^(-n!), {n, 2, Infinity}] - 
     567067016846573451010485778130831*
      Sum[80^(-n!), {n, 2, Infinity}] - 
     1905831513124390141890451640600611*
      Sum[81^(-n!), {n, 2, Infinity}] - 
     5136597947331669055009371904973487*
      Sum[82^(-n!), {n, 2, Infinity}] + 
     912278368494920565761271769690129*
      Sum[83^(-n!), {n, 2, Infinity}] - 
     2580979677015581716819042733783251*
      Sum[84^(-n!), {n, 2, Infinity}] + 
     1884158460408959578540033438166537*
      Sum[85^(-n!), {n, 2, Infinity}] + 
     2996809848467580062948210521300363*
      Sum[86^(-n!), {n, 2, Infinity}] + 
     2547118062655141771555127378895892*
      Sum[87^(-n!), {n, 2, Infinity}] + 
     122733378092474394591379091380222*
      Sum[88^(-n!), {n, 2, Infinity}] + 
     1609043837874589833719447903600838*
      Sum[89^(-n!), {n, 2, Infinity}] + 
     706449525697658734698912642263703*
      Sum[90^(-n!), {n, 2, Infinity}] + 
     331198650888790532168855884736297*
      Sum[91^(-n!), {n, 2, Infinity}] + 
     616901082829008843727297647565846*
      Sum[92^(-n!), {n, 2, Infinity}] + 
     2407854441179185932069643380268222*
      Sum[93^(-n!), {n, 2, Infinity}] - 
     4494561604681894784950422947849268*
      Sum[94^(-n!), {n, 2, Infinity}] + 
     1259577304594505752616397860280623*
      Sum[95^(-n!), {n, 2, Infinity}] - 
     2564935607306630357867809604407419*
      Sum[96^(-n!), {n, 2, Infinity}])/
   230024844450836751070309032939613, 
   3000]
giving
  Out[49]= 1 36025200332815066380729833521872476571420563018384745339137125938852363572682438`47.\
36565286514424*^-3002
Here is the 4,000 approximation:
N[m - (-296516481636968137503982279733117020027871*
      Sum[3^(-n!), {n, 2, Infinity}] + 
     325661615276655660175959176674077806917110*
            Sum[4^(-n!), {n, 2, Infinity}] + 
     642182094925939713175056356584465598954027*
      Sum[5^(-n!), {n, 2, Infinity}] + 
     601175274312643299513368500777196611943043*
      Sum[6^(-n!), {n, 2, Infinity}] + 
     461071564223118140831888034215659217102634*
            Sum[7^(-n!), {n, 2, Infinity}] - 
     46056184702533685913819676113042970084596*
      Sum[8^(-n!), {n, 2, Infinity}] + 
     279339004802534787952844028108115284244029*
      Sum[9^(-n!), {n, 2, Infinity}] - 
     299266395268565444689230937067754075583779*
            Sum[10^(-n!), {n, 2, Infinity}] - 
     465234809034158007809899570315803804300290*
      Sum[11^(-n!), {n, 2, Infinity}] + 
     285887132280583324375825088698929314025198*
      Sum[12^(-n!), {n, 2, Infinity}] - 
     1455153254962389166044713884804999761815895*
            Sum[13^(-n!), {n, 2, Infinity}] - 
     433114104837923880113595542995205621923404*
      Sum[14^(-n!), {n, 2, Infinity}] + 
     1160117914615393859326075479663370802329893*
      Sum[15^(-n!), {n, 2, Infinity}] - 
     847974925978145426909219295179634996686481*
            Sum[16^(-n!), {n, 2, Infinity}] - 
     478039072552888313172646196547768919885589*
      Sum[17^(-n!), {n, 2, Infinity}] - 
     1207220432365216840785401069506724372409135*
      Sum[18^(-n!), {n, 2, Infinity}] - 
     565442430159872587593563683618559838970756*
            Sum[19^(-n!), {n, 2, Infinity}] + 
     281004860950920620115935860078699244770248*
      Sum[20^(-n!), {n, 2, Infinity}] + 
     38542239404878995475716101692658191802366*
      Sum[21^(-n!), {n, 2, Infinity}] + 
     1442550945203909873532394738550482603093249*
            Sum[22^(-n!), {n, 2, Infinity}] - 
     1070315093526954824158169515996581349047557*
      Sum[23^(-n!), {n, 2, Infinity}] - 
     1196569785451215366214358216221843708950368*
      Sum[24^(-n!), {n, 2, Infinity}] - 
     1504057272276809031352388906961647123416340*
            Sum[25^(-n!), {n, 2, Infinity}] + 
     475291034780375689238862608191953323145543*
      Sum[26^(-n!), {n, 2, Infinity}] - 
     524027840995878115513925912794868447867202*
      Sum[27^(-n!), {n, 2, Infinity}] - 
     1620441974573474591410837709104326096167725*
            Sum[28^(-n!), {n, 2, Infinity}] - 
     414214539885862686599974983033151068422599*
      Sum[29^(-n!), {n, 2, Infinity}] + 
     559985517658515157527015054675982392369751*
      Sum[30^(-n!), {n, 2, Infinity}] + 
     487621074248268136802789768671137109262588*
            Sum[31^(-n!), {n, 2, Infinity}] + 
     674666619828450995162006462639617999407097*
      Sum[32^(-n!), {n, 2, Infinity}] - 
     106618498602952986491811414739566870171557*
      Sum[33^(-n!), {n, 2, Infinity}] + 
     1168555124211830147037898399967040382528817*
            Sum[34^(-n!), {n, 2, Infinity}] + 
     85390599906882793536181196132857692177667*
      Sum[35^(-n!), {n, 2, Infinity}] + 
     569708755874101365117562354940363507455858*
      Sum[36^(-n!), {n, 2, Infinity}] - 
     435805753404222631106858418183069441499085*
            Sum[37^(-n!), {n, 2, Infinity}] - 
     100632304065941203378884812209693888341737*
      Sum[38^(-n!), {n, 2, Infinity}] + 
     175980026251533802235364343828740109328330*
      Sum[39^(-n!), {n, 2, Infinity}] - 
     203093029693440514891257626039459460579530*
            Sum[40^(-n!), {n, 2, Infinity}] - 
     527109494975226274138625409584388590824167*
      Sum[41^(-n!), {n, 2, Infinity}] - 
     1441919975136263248521894296063643037329957*
      Sum[42^(-n!), {n, 2, Infinity}] + 
     302034343438868384200878876044014773620801*
            Sum[43^(-n!), {n, 2, Infinity}] + 
     583248854885837765648122572543150789918959*
      Sum[44^(-n!), {n, 2, Infinity}] + 
     702270194902490380525021700597036955614413*
      Sum[45^(-n!), {n, 2, Infinity}] - 
     500436526244688040036598186854976926921324*
            Sum[46^(-n!), {n, 2, Infinity}] + 
     81489006025013640398934425492602897258138*
      Sum[47^(-n!), {n, 2, Infinity}] - 
     761473920288312286531262650480401117313772*
      Sum[48^(-n!), {n, 2, Infinity}] - 
     1034990444893569446002055543630756560017555*
            Sum[49^(-n!), {n, 2, Infinity}] - 
     754253538292494367301525764238807361811031*
      Sum[50^(-n!), {n, 2, Infinity}] - 
     1132795850299834123210924644846840733101239*
      Sum[51^(-n!), {n, 2, Infinity}] + 
     2387010927143877767508686859158595028391373*
            Sum[52^(-n!), {n, 2, Infinity}] - 
     1089822591277202578314471461685208924013469*
      Sum[53^(-n!), {n, 2, Infinity}] - 
     81001683977437981798666572764812171960730*
      Sum[54^(-n!), {n, 2, Infinity}] - 
     582248537457995534060569443329206686787816*
            Sum[55^(-n!), {n, 2, Infinity}] + 
     168776064302334723300910242823139170872068*
      Sum[56^(-n!), {n, 2, Infinity}] - 
     424077533292026559795307574966795337212312*
      Sum[57^(-n!), {n, 2, Infinity}] + 
     1109947769465243875535508831964972433450393*
            Sum[58^(-n!), {n, 2, Infinity}] + 
     612691804838323729773604875710797428704379*
      Sum[59^(-n!), {n, 2, Infinity}] - 
     846613643602017244023404751070377238390310*
      Sum[60^(-n!), {n, 2, Infinity}] - 
     637234398046077593684936948711478827364827*
            Sum[61^(-n!), {n, 2, Infinity}] - 
     595473419173144376910893545292289278055168*
      Sum[62^(-n!), {n, 2, Infinity}] - 
     798382236515911107795355064641213265865957*
      Sum[63^(-n!), {n, 2, Infinity}] - 
     1475710630751426353616979652407251998437441*
            Sum[64^(-n!), {n, 2, Infinity}] - 
     349266086857445890482716730556079686616657*
      Sum[65^(-n!), {n, 2, Infinity}] + 
     576297702314586207635300890940428731650513*
      Sum[66^(-n!), {n, 2, Infinity}] + 
     64424778631246518288433825435442342473108*
            Sum[67^(-n!), {n, 2, Infinity}] + 
     768355660157040286478201814231161522585435*
      Sum[68^(-n!), {n, 2, Infinity}] + 
     293710790604950219816671224005902252977446*
      Sum[69^(-n!), {n, 2, Infinity}] - 
     559797054427464244707254151567534633845493*
            Sum[70^(-n!), {n, 2, Infinity}] + 
     80950405776998237843876379200957275189067*
      Sum[71^(-n!), {n, 2, Infinity}] + 
     1670729414137120803674093465162507318808519*
      Sum[72^(-n!), {n, 2, Infinity}] + 
     775685504163875455988543406432695543816217*
            Sum[73^(-n!), {n, 2, Infinity}] + 
     1333091995709003174575758585461773893418308*
      Sum[74^(-n!), {n, 2, Infinity}] - 
     155872950652287384316462697258741573600564*
      Sum[75^(-n!), {n, 2, Infinity}] + 
     1012411988025439131263676384839491452505632*
            Sum[76^(-n!), {n, 2, Infinity}] + 
     1435991513389482138446348675629225179237248*
      Sum[77^(-n!), {n, 2, Infinity}] - 
     163117194140768456768697927667437080083367*
      Sum[78^(-n!), {n, 2, Infinity}] - 
     1894571430791935332300955306245180675566119*
            Sum[79^(-n!), {n, 2, Infinity}] - 
     88650069624075571861901184013020969336140*
      Sum[80^(-n!), {n, 2, Infinity}] - 
     2443195669827387130450675747324794999468278*
      Sum[81^(-n!), {n, 2, Infinity}] - 
     445403791149756764405424065112370443906832*
            Sum[82^(-n!), {n, 2, Infinity}] + 
     1011876040895889660018147477114342871487124*
      Sum[83^(-n!), {n, 2, Infinity}] - 
     841225667122861617814628363282657839089313*
      Sum[84^(-n!), {n, 2, Infinity}] + 
     781153505932427407408615277783615012304737*
            Sum[85^(-n!), {n, 2, Infinity}] - 
     1512669741220256920604392332262610689126748*
      Sum[86^(-n!), {n, 2, Infinity}] - 
     116806211318565735630179723946845979649289*
      Sum[87^(-n!), {n, 2, Infinity}] + 
     429130091032045229595229240522857578374793*
            Sum[88^(-n!), {n, 2, Infinity}] + 
     506765034962670771473975504854800595831172*
      Sum[89^(-n!), {n, 2, Infinity}] - 
     879274842685359858085342642938644291494265*
      Sum[90^(-n!), {n, 2, Infinity}] - 
     74882381833281682041429986677690145192329*
            Sum[91^(-n!), {n, 2, Infinity}] - 
     1481962754796105396642750584065054290318576*
      Sum[92^(-n!), {n, 2, Infinity}] + 
     371582750848581648295884969326092328244938*
      Sum[93^(-n!), {n, 2, Infinity}] - 
     548940842526326295585707606326385101045388*
            Sum[94^(-n!), {n, 2, Infinity}] - 
     214364159079515020789428860678593442975390*
      Sum[95^(-n!), {n, 2, Infinity}] - 
     792746436246894058263311867715612724830428*
      Sum[96^(-n!), {n, 2, Infinity}] + 
     98779136320327876056553220251060452284968*
            Sum[97^(-n!), {n, 2, Infinity}] + 
     420817031258715595750978255792960491285033*
      Sum[98^(-n!), {n, 2, Infinity}] + 
     133685347739575372427537403082058930459109*
      Sum[99^(-n!), {n, 2, Infinity}] + 
     624039311167296059305190395710287624563274*
            Sum[100^(-n!), {n, 2, Infinity}] - 
     1033617019679927139078081654715284819642299*
      Sum[101^(-n!), {n, 2, Infinity}] - 
     684584444208170176786209670810376971046901*
      Sum[102^(-n!), {n, 2, Infinity}])/
   85378145960320201007017729300346246766531, 5000]
				
					
				
				
					
					
						
							
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