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 A135884 #2 Mar 30 2012 18:37:07
%S A135884 1,4,26,216,2171,25628,348050,5352788,92056223,1752149568,36591725976,
%T A135884 832352590164,20493399785598,543168774618834,15424012639825146,
%U A135884 467276557333020682,15046702103550879196,513273141160665106150
%N A135884 Column 3 of triangle A135880.
%e A135884 Equals column 3 of triangle P=A135880:
%e A135884 1;
%e A135884 1, 1;
%e A135884 2, 2, 1;
%e A135884 6, 7, 3, 1;
%e A135884 25, 34, 15, 4, 1;
%e A135884 138, 215, 99, 26, 5, 1;
%e A135884 970, 1698, 814, 216, 40, 6, 1;
%e A135884 8390, 16220, 8057, 2171, 400, 57, 7, 1; ...
%e A135884 where column k of P^2 equals column 0 of P^(2k+2)
%e A135884 such that column 0 of P^2 equals column 0 of P shift left.
%o A135884 (PARI) {a(n)=local(P=Mat(1),R,PShR);if(n==0,1,for(i=0,n+2, PShR=matrix(#P,#P, r,c, if(r>=c,if(r==c,1,if(c==1,0,P[r-1,c-1]))));R=P*PShR; R=matrix(#P+1, #P+1, r,c, if(r>=c, if(r<#P+1,R[r,c], if(c==1,(P^2)[ #P,1],(P^(2*c-1))[r-c+1,1])))); P=matrix(#R, #R, r,c, if(r>=c, if(r<#R,P[r,c], (R^c)[r-c+1,1]))));P[n+4,4])}
%Y A135884 Cf. A135880; other columns: A135881, A135882, A135883.
%K A135884 nonn
%O A135884 0,2
%A A135884 _Paul D. Hanna_, Dec 15 2007