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 A381779 #7 Mar 07 2025 10:47:40
%S A381779 1,2,11,95,977,11028,132029,1646428,21155077,278127359,3723466202,
%T A381779 50586670945,695676081162,9665426437561,135464096419620,
%U A381779 1912922793362142,27190770354633287,388734441118885467,5586079818959767743,80638973170989453862,1168864771263296930809
%N A381779 G.f. A(x) satisfies A(x) = (1 + x*A(x)) * C(x*A(x)^3), where C(x) is the g.f. of A000108.
%F A381779 a(n) = Sum_{k=0..n} binomial(n+4*k+1,k) * binomial(n+2*k+1,n-k)/(n+4*k+1).
%o A381779 (PARI) a(n) = sum(k=0, n, binomial(n+4*k+1, k)*binomial(n+2*k+1, n-k)/(n+4*k+1));
%Y A381779 Cf. A054727, A381778.
%Y A381779 Cf. A000108.
%K A381779 nonn
%O A381779 0,2
%A A381779 _Seiichi Manyama_, Mar 07 2025