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 A377489 #5 Oct 30 2024 08:04:24
%S A377489 1,2,24,548,18996,889532,52623924,3767367788,316781141316,
%T A377489 30608709436412,3342279339791124,407043376061484428,
%U A377489 54704971792071412836,8042679084840031176092,1284038419974274852278324,221234151594672691543079468,40916180234895561309469607556
%N A377489 E.g.f. satisfies A(x) = 1/(1 - A(x)^2 * (exp(x) - 1))^2.
%F A377489 E.g.f.: B(x)^2, where B(x) is the e.g.f. of A377451.
%F A377489 a(n) = 2 * Sum_{k=0..n} (5*k+1)!/(4*k+2)! * Stirling2(n,k).
%o A377489 (PARI) a(n) = 2*sum(k=0, n, (5*k+1)!/(4*k+2)!*stirling(n, k, 2));
%Y A377489 Cf. A377451, A377454.
%K A377489 nonn
%O A377489 0,2
%A A377489 _Seiichi Manyama_, Oct 29 2024