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 A166886 #2 Mar 30 2012 18:37:18
%S A166886 1,2,9,62,593,7266,108720,1922166,39212154,906623004,23429034168,
%T A166886 669203550906,20935080981744,711872134399868,26142553369667634,
%U A166886 1031146768716808794,43475757877044427198,1951261759908828697902
%N A166886 Column 2 of triangle A166884.
%C A166886 Triangle A166884 transforms diagonals in the triangle A166880 of coefficients in the successive iterations of x+x^2+x^3.
%o A166886 (PARI) {a(n)=local(F=x, M, N, P, m=n+1); M=matrix(m+2, m+2, r, c, F=x; for(i=1, r+c-2, F=subst(F, x, x+x^2+x^3+x*O(x^(m+2)))); polcoeff(F, c)); N=matrix(m+1, m+1, r, c, M[r, c]); P=matrix(m+1, m+1, r, c, M[r+1, c]); (P~*N~^-1)[n+2, 2]}
%Y A166886 Cf. A166880, A166884, A166885, A166887.
%K A166886 nonn
%O A166886 1,2
%A A166886 _Paul D. Hanna_, Nov 21 2009