A355986 - OEIS

%I #13 Jul 22 2022 10:13:14

%S 1,3,8,28,125,731,5052,40352,362917,3628935,39916936,479002360,

%T 6227021561,87178296283,1307674373184,20922789928484,355687428136485,

%U 6402373706091651,121645100409195652,2432902008180269688,51090942171713074013,1124000727777647602015

%N a(n) = Sum_{k=1..n} floor(n/k)!.

%e a(6) = 6! + 3! + 2! + 1! + 1! + 1! = 731.

%t a[n_] := Sum[Floor[n/k]!, {k, 1, n}]; Array[a, 22] (* _Amiram Eldar_, Jul 22 2022 *)

%o (PARI) a(n) = sum(k=1, n, (n\k)!);

%Y Cf. A007489, A060832, A081123.

%K nonn,easy

%O 1,2

%A _Seiichi Manyama_, Jul 22 2022