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 A086631 #12 Jul 30 2023 09:45:24
%S A086631 1,2,4,10,29,92,310,1088,3931,14518,54551,207856,801202,3118532,
%T A086631 12239732,48385852,192483953,769974110,3095236066,12497442266,
%U A086631 50660112478,206093561590,841151382755,3443278744832,14133534466258
%N A086631 Antidiagonal sums of square table A086629.
%H A086631 Seiichi Manyama, <a href="/A086631/b086631.txt">Table of n, a(n) for n = 0..1000</a>
%F A086631 G.f.: A(x) = 1/(1-x)^2 + x^2*A(x)^3.
%F A086631 a(n) = Sum_{k=0..floor(n/2)} binomial(n+2*k+1,4*k+1) * binomial(3*k,k) / (2*k+1). - _Seiichi Manyama_, Jul 30 2023
%o A086631 (PARI) a(n) = sum(k=0, n\2, binomial(n+2*k+1, 4*k+1)*binomial(3*k, k)/(2*k+1)); \\ _Seiichi Manyama_, Jul 30 2023
%Y A086631 Cf. A001764, A086615, A086629 (table), A086630 (diagonal).
%K A086631 nonn
%O A086631 0,2
%A A086631 _Paul D. Hanna_, Jul 24 2003