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 A107669 #3 Mar 30 2012 18:36:46
%S A107669 1,1,5,51,809,17575,486460,16384260,650574249,29762953831,
%T A107669 1541719486081,89201504309927,5702038255950404,399105271607867940,
%U A107669 30359621863987241460,2494052823831234355340,220067051126228849480649
%N A107669 a(n) = A107668(n)/(n+1)^2.
%o A107669 (PARI) {a(n)=local(A);if(n==0,n+1,A=(n+1)*x+x*O(x^n); for(k=0,n,A+=polcoeff(A,k)*x^k*(n+1-prod(i=0,k,1+(i-n-1)*x))); polcoeff(A,n)/(n+1)^2)}
%Y A107669 Cf. A107667, A107668, A107670.
%K A107669 nonn
%O A107669 0,3
%A A107669 _Paul D. Hanna_, Jun 07 2005