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 A107888 #5 Nov 26 2016 18:07:23
%S A107888 1,3,18,154,1689,22518,353211,6373053,130079286,2964644430,
%T A107888 74663152896,2060033160771,61821589542329,2005535153907369,
%U A107888 69957741972993120,2611812581931916545,103938147849788867430,4392991505873072541159
%N A107888 Column 4 of triangle A107884.
%F A107888 G.f.: 1 = Sum_{k>=0} a(k)*x^k*(1-x)^((k+3)*(k+4)/2-3).
%e A107888 1 = 1*(1-x)^3 + 3*x*(1-x)^7 + 18*x^2*(1-x)^12 +
%e A107888 154*x^3*(1-x)^18 + 1689*x^4*(1-x)^25 + 22518*x^5*(1-x)^33 +...
%t A107888 a[ n_, k_: 0, j_: 3] := If[n < 1, Boole[n >= 0], a[ n, k, j] = Sum[ a[ n - 1, i, j + 1], {i, k + j}]]; (* _Michael Somos_, Nov 26 2016 *)
%o A107888 (PARI) {a(n)=polcoeff(1-sum(k=0,n-1,a(k)*x^k*(1-x+x*O(x^n))^((k+3)*(k+4)/2-3)),n)}
%Y A107888 Cf. A107884, A107885, A107886, A107887.
%K A107888 nonn
%O A107888 0,2
%A A107888 _Paul D. Hanna_, Jun 05 2005