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 A107881 #3 Mar 30 2012 18:36:46
%S A107881 1,2,3,7,26,141,1034,9693,111522,1528112,24372513,444461496,
%T A107881 9135985760,209223309377,5286985099830,146225910921737,
%U A107881 4395973641599418,142794782804641965,4985911547339049132,186284207595651780174
%N A107881 Column 0 of triangle A107880.
%F A107881 G.f.: 1 = Sum_{k>=0} a(k)*x^k*(1-x)^(2 + k*(k-1)/2).
%e A107881 1 = 1*(1-x)^2 + 2*x*(1-x)^2 + 3*x^2*(1-x)^3 +
%e A107881 7*x^3*(1-x)^5 + 26*x^4*(1-x)^8 + 141*x^5*(1-x)^12 +...
%o A107881 (PARI) {a(n)=polcoeff(1-sum(k=0,n-1,a(k)*x^k*(1-x+x*O(x^n))^(2+k*(k-1)/2)),n)}
%Y A107881 Cf. A107880, A107882, A107883.
%K A107881 nonn
%O A107881 0,2
%A A107881 _Paul D. Hanna_, Jun 04 2005