# User Portlet

Ed Pegg
Discussions
Here's a list of hits and near misses. The first hit is (43+0)(43+4) = 2021. The first near miss is (53+0)(53+8) = 3233. {{43,{0,4}}, {4999493,{0,14}}, {891077215721081784886888257701070827,{0,2}},...
Awhile ago we added GraphData[{"UnitDistance", {21, 2}}] to Mathematica. Graph[GraphData[{"UnitDistance", {21, 2}}], VertexLabels -> "Name"] ![heptagon bracing][1] I found the graph while researching unit-distance graphs...
Todd, how would the 3D diagonal CA be set up? It seems obvious that we should find out if a "1D" cellular automaton can build a menger sponge.
MissingÂ—one square to four, or one equilateral triangle to four. How about one square to five? AlgebraicSubstitutionTiling[{1,{{-3,-1},{-3,1},{-1,-3},{-1,-1},{-1,1},{-1,3},{1,-3},{1,-1},{1,1},{1,3},{3,-1},{3,1}}, {{1,6,12,7}->...
Could this be used to make the [plesiohedra][1]? [1]: https://refubium.fu-berlin.de/handle/fub188/10176
I fixed the links... [https://demonstrations.wolfram.com/MrsPerkinssQuilts/][1] [1]: https://demonstrations.wolfram.com/MrsPerkinssQuilts/
FiniteGroupData is missing a few group generations, so I've filled in some holes. One of the groups is Frobenius 21. ...
What is the smallest set so that differences of members of the set give all values from $1$ to $n$? This is a famous problem worked on by [Paul Erd?s](https://en.wikipedia.org/wiki/Paul_Erd%C5%91s), [Marcel J. E....
How to solve something like this? Consider the problem of covering the largest possible equilateral triangle with two unit squares. I make a sketch in Geometer's Sketchpad first. ![two squares][1] Then put the equations right into...
Manipulate[Module[{sol2}, sol2=ParametricNDSolve[{x'[t]==Cos[t],y'[t]==Sin[t],z'[t]==b*1/4,x[0]==0,y[0]==1,z[0]==0},{x,y,z},{t,0,100},{a}]; ...