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 A228906 #6 May 26 2025 23:50:47
%S A228906 1,2,7,62,1031,24782,774180,29763855,1359654560,71984907423,
%T A228906 4335406418694,292753300447894,21909289407621069,1800106653483146619,
%U A228906 161097567109713138999,15599377878403186676330,1625083531855929644443019,181238001661004834528467994,21545324993880123460418461719
%N A228906 A diagonal of triangle A228904.
%C A228906 Triangle A228904 is defined by g.f.: exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n*k, k^2) * y^k ).
%o A228906 (PARI) {a(n)=polcoeff(polcoeff(exp(sum(m=1, n, x^m/m*sum(j=0, m, binomial(m*j, j^2)*y^j))+x*O(x^n)), n, x), n-1, y)}
%o A228906 for(n=1, 20, print1(a(n), ", "))
%Y A228906 Cf. A228904.
%K A228906 nonn
%O A228906 1,2
%A A228906 _Paul D. Hanna_, Sep 07 2013