This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A113083 #3 Mar 30 2012 18:36:51
%S A113083 1,2,21,724,75695,23694838,22239639177,62747494950248,
%T A113083 532868670719193651,13624738004791751175370,
%U A113083 1048678107774203901392276461,242892250870416811233766661498812
%N A113083 Diagonal of square table A113081; also, a(n) equals the n-th term in column 0 of the matrix (n+1)-th power of triangle A113084.
%o A113083 (PARI) {a(n,q=3)=local(M=matrix(n+1,n+1));for(r=1,n+1, for(c=1,r, M[r,c]=if(r==c,1,if(c>1,(M^q)[r-1,c-1])+(M^q)[r-1,c]))); return(if(n<1,0,(M^n)[n,1]))}
%Y A113083 Cf. A113081, A113084.
%K A113083 nonn
%O A113083 1,2
%A A113083 _Paul D. Hanna_, Oct 14 2005