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 A228903 #9 Feb 24 2025 08:52:05
%S A228903 1,3,45,2905,411500,100545716,37614371968,19977489354808,
%T A228903 14291976911388733,13248449270832615473,15445843697030022753539,
%U A228903 22118947642938636936616739,38166279965353127309979185861,78098472647949324804924786089941,186993874842690500015923551395259661
%N A228903 Second diagonal of triangle A228902.
%C A228903 Triangle A228902 is defined by g.f.: exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n^2, k^2) * y^k ).
%o A228903 (PARI) {a(n)=polcoeff(polcoeff(exp(sum(m=1, n, x^m/m*sum(j=0, m, binomial(m^2, j^2)*y^j))+x*O(x^n)), n, x), n-1, y)}
%o A228903 for(n=1, 20, print1(a(n), ", "))
%Y A228903 Cf. A228902.
%K A228903 nonn
%O A228903 1,2
%A A228903 _Paul D. Hanna_, Sep 07 2013