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 A347994 #7 Sep 24 2021 02:52:56
%S A347994 0,1,4,30,296,3720,56652,1014832,20909520,487198080,12667470740,
%T A347994 363607605504,11420819358456,389646915374080,14349217119054300,
%U A347994 567315485527234560,23967624180805666208,1077568488585047605248,51369752823292604784420,2588268388538639982592000
%N A347994 a(n) = n! * Sum_{k=1..n-1} (-1)^(k+1) * n^(n-k-2) / (n-k-1)!.
%F A347994 E.g.f.: -LambertW(-x) - log(1 - LambertW(-x)).
%F A347994 a(n) = A134095(n) / n.
%t A347994 Table[n! Sum[(-1)^(k + 1) n^(n - k - 2)/(n - k - 1)!, {k, 1, n - 1}], {n, 1, 20}]
%t A347994 nmax = 20; CoefficientList[Series[-LambertW[-x] - Log[1 - LambertW[-x]], {x, 0, nmax}], x] Range[0, nmax]! // Rest
%o A347994 (PARI) a(n) = n! * sum(k=1, n-1, (-1)^(k+1)*n^(n-k-2)/(n-k-1)!); \\ _Michel Marcus_, Sep 23 2021
%Y A347994 Cf. A000169, A000435, A133297, A134095, A347993.
%K A347994 nonn
%O A347994 1,3
%A A347994 _Ilya Gutkovskiy_, Sep 23 2021