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A316297
a(n) = n! times the denominator of the n-th harmonic number H(n).
1
1, 4, 36, 288, 7200, 14400, 705600, 11289600, 914457600, 9144576000, 1106493696000, 13277924352000, 2243969215488000, 31415569016832000, 471233535252480000, 15079473128079360000, 4357967734014935040000, 26147806404089610240000, 9439358111876349296640000
OFFSET
1,2
FORMULA
a(n) = A000142(n) * A002805(n).
EXAMPLE
a(4) = 4! * A002805(4) = 24 * 12 = 288.
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 *)
PROG
(PARI) a(n) = n! * denominator(sum(k=1, n, 1/k)); \\ Michel Marcus, Aug 12 2018
KEYWORD
nonn
AUTHOR
Matthew Campbell, Jun 29 2018
STATUS
approved