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a(n) = Sum_{k=0..n} (n - k)! * (n - 1)^k. Row sums of A350269.
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%I #8 Dec 25 2021 14:51:48

%S 1,1,4,22,168,1720,22670,368784,7134148,159416704,4027395330,

%T 113235212800,3501763366904,118024658758656,4303855119215782,

%U 168777440194263040,7081468496171815500,316501174908316647424,15010862087643791689322,752916261526858377363456

%N a(n) = Sum_{k=0..n} (n - k)! * (n - 1)^k. Row sums of A350269.

%t a[1] = 1; a[n_] := Sum[(n - k)! * (n - 1)^k, {k, 0, n}]; Array[a, 20, 0] (* _Amiram Eldar_, Dec 25 2021 *)

%o (PARI) a(n) = sum(k=0, n, (n-k)!*(n-1)^k); \\ _Michel Marcus_, Dec 25 2021

%Y Cf. A350269.

%K nonn

%O 0,3

%A _Peter Luschny_, Dec 25 2021