A316297 a(n) = n! times the denominator of the n-th harmonic number H(n).

1, 4, 36, 288, 7200, 14400, 705600, 11289600, 914457600, 9144576000, 1106493696000, 13277924352000, 2243969215488000, 31415569016832000, 471233535252480000, 15079473128079360000, 4357967734014935040000, 26147806404089610240000, 9439358111876349296640000

Offset: 1

Author

Matthew Campbell, Jun 29 2018

Keywords

• nonn

Examples

			a(4) = 4! * A002805(4) = 24 * 12 = 288.
		

Crossrefs

Cf. A000142, A001008, A002805, A027611, A027612, A124837, A124838.

Programs

Maple

H:= proc(n) H(n):= 1/n +`if`(n=1, 0, H(n-1)) end:
a:= n-> denom(H(n))*n!:
seq(a(n), n=1..20);  # Alois P. Heinz, Jul 21 2018

Mathematica

a[n_] := n! Denominator@HarmonicNumber@n; Array[a, 18] (* Robert G. Wilson v, Jun 30 2018 *)

PARI

a(n) = n! * denominator(sum(k=1, n, 1/k)); \\ Michel Marcus, Aug 12 2018

Formula

a(n) = A000142(n) * A002805(n).