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 A381428 #11 Feb 24 2025 04:19:08
%S A381428 1,1,6,73,1344,33481,1054656,40223233,1802385024,92827015921,
%T A381428 5403527705856,350854589607193,25142008355656704,1971003462240791161,
%U A381428 167802783944207917056,15417877986778302551953,1520661128893781018640384,160249491538400609431567201,17969682580669053325124960256
%N A381428 E.g.f. A(x) satisfies A(x) = 1/( 1 - sinh(x) * A(x)^2 ).
%F A381428 a(n) = Sum_{k=0..n} k! * binomial(3*k+1,k)/(3*k+1) * A136630(n,k).
%o A381428 (PARI) a136630(n, k) = 1/(2^k*k!)*sum(j=0, k, (-1)^(k-j)*(2*j-k)^n*binomial(k, j));
%o A381428 a(n) = sum(k=0, n, k!*binomial(3*k+1,k)/(3*k+1)*a136630(n, k));
%Y A381428 Cf. A006154, A295254, A381429.
%Y A381428 Cf. A136630.
%K A381428 nonn
%O A381428 0,3
%A A381428 _Seiichi Manyama_, Feb 23 2025