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 A166885 #2 Mar 30 2012 18:37:18
%S A166885 1,1,3,15,114,1159,14838,229401,4159662,86580636,2034850425,
%T A166885 53303009286,1539990513588,48648616439496,1668228105283302,
%U A166885 61715049142446537,2450018515737072792,103892256368706869356,4686744256645813560957
%N A166885 Column 1 of triangle A166884.
%C A166885 Triangle A166884 transforms diagonals in the triangle A166880 of coefficients in the successive iterations of x+x^2+x^3.
%o A166885 (PARI) {a(n)=local(F=x, M, N, P, m=n); 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+1, 1]}
%Y A166885 Cf. A166880, A166884, A166886, A166887.
%K A166885 nonn
%O A166885 1,3
%A A166885 _Paul D. Hanna_, Nov 21 2009