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 A377956 #6 Nov 12 2024 09:01:56
%S A377956 1,5,23,103,473,2261,11215,57863,309713,1715653,9831911,58058375,
%T A377956 353546473,2210900693,14215319903,93610866151,632159025185,
%U A377956 4362925851653,30809311250743,221958273142823,1632956199823481,12238229941781845,93509510960341103,726913018468699463
%N A377956 a(n) = n! * Sum_{k=0..n} binomial(k+4,n-k) / k!.
%F A377956 E.g.f.: (1 + x)^4 * exp(x + x^2).
%F A377956 a(n) = -(n-6)*a(n-1) + 3*(n-1)*a(n-2) + 2*(n-1)*(n-2)*a(n-3) for n > 2.
%o A377956 (PARI) a(n) = n!*sum(k=0, n, binomial(k+4, n-k)/k!);
%Y A377956 Cf. A018191, A047974, A377954, A377955.
%K A377956 nonn,easy
%O A377956 0,2
%A A377956 _Seiichi Manyama_, Nov 12 2024