# How to write an embedded sum series in Wolfram Alpha?

Posted 2 months ago
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 I am trying to write the following mathematical expression on wolfram alpha but failing , i do not know how to embedded the sum series into another as per the expression. here is what i have so far:[(2^k87^(2k))/(622^(2k)k!)[1-exp(-215^2/622^2)sum ((2^j15^(2j))/(622^(2j)*j!)), j=0 to k]]inserting this into wolfram alpha i get: i dont know how to add the other sum term into the expression... note: d=87 w=622 a=15
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Posted 2 months ago
 I wasn't able to do the nested sum in a single step, but breaking it into two slightly simpler nested sums might be valid. I also wasn't able to sum k from zero to infinity in the second summation without it timing out or saying that it could not understand my input, but summing k from zero to 20 looks like that is very very close to the infinite sum, even k from 0 to 6 gives almost the same result.. Sum[2^k 87^(2 k)/(622^(2 k) k!)*1, {k,0,Infinity}]+ Sum[2^k 87^(2 k)/(622^(2 k) k!)*-Exp[-215^2/622^2]*Sum[2^j*15^(2*j)/(622^(2*j) j!), {j,0,k}], {k,0,20}] See if you can understand how I rearranged that and if you think you can justify the changes I made..
Posted 2 months ago
 Thanks a bunch! that works! Spent like 5 hours yesterday on it...