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 A351779 #10 Feb 19 2022 13:55:57
%S A351779 1,-1,4,-63,2288,-138525,12381084,-1528482823,249005711296,
%T A351779 -51739455340953,13353206066063900,-4190486732316600771,
%U A351779 1571373340568392914288,-693899460077821703051125,356404409990391961980227068,-210670220153918100996704166975
%N A351779 a(n) = n! * Sum_{k=0..n} (-n)^(n-k) * (n-k)^k/k!.
%F A351779 a(n) = n! * [x^n] 1/(1 + n*x*exp(x)).
%o A351779 (PARI) a(n) = n!*sum(k=0, n, (-n)^(n-k)*(n-k)^k/k!);
%Y A351779 Main diagonal of A351776.
%Y A351779 Cf. A351765, A351780.
%K A351779 sign
%O A351779 0,3
%A A351779 _Seiichi Manyama_, Feb 19 2022