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 A343841 #9 May 07 2021 08:06:26
%S A343841 1,1,-1,-5,15,56,-455,-237,16947,-64220,-529494,6833608,-8606015,
%T A343841 -459331677,4335744673,6800310151,-518075832085,4315086396640,
%U A343841 19931595013738,-812870258798156,6648395876520816,46852711038750520,-1752440325584024944,15485712825845269456
%N A343841 a(n) = Sum{k=0..n} (-1)^(n-k)*binomial(n, k)*Stirling2(n, k).
%p A343841 a := n -> add((-1)^(n-k)*binomial(n, k)*Stirling2(n, k), k=0..n):
%p A343841 seq(a(n), n = 0..24);
%t A343841 a[n_] := Sum[(-1)^(n - k) * Binomial[n, k] * StirlingS2[n, k], {k, 0, n}]; Array[a, 24, 0] (* _Amiram Eldar_, May 07 2021 *)
%o A343841 (PARI) a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*stirling(n, k, 2)); \\ _Michel Marcus_, May 07 2021
%Y A343841 Cf. A048993, A122455, A211210, A317274.
%K A343841 sign
%O A343841 0,4
%A A343841 _Peter Luschny_, May 04 2021