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%I #56 Aug 12 2018 04:04:25
%S 1,4,36,288,7200,14400,705600,11289600,914457600,9144576000,
%T 1106493696000,13277924352000,2243969215488000,31415569016832000,
%U 471233535252480000,15079473128079360000,4357967734014935040000,26147806404089610240000
%N a(n) = n! times the denominator of the n-th harmonic number H(n).
%F a(n) = A000142(n) * A002805(n).
%e a(4) = 4! * A002805(4) = 24 * 12 = 288.
%p H:= proc(n) H(n):= 1/n +`if`(n=1, 0, H(n-1)) end:
%p a:= n-> denom(H(n))*n!:
%p seq(a(n), n=1..20); # _Alois P. Heinz_, Jul 21 2018
%t a[n_] := n! Denominator@HarmonicNumber@n; Array[a, 18] (* _Robert G. Wilson v_, Jun 30 2018 *)
%o (PARI) a(n) = n! * denominator(sum(k=1, n, 1/k)); \\ _Michel Marcus_, Aug 12 2018
%Y Cf. A000142, A001008, A002805, A027611, A027612, A124837, A124838.
%K nonn
%O 1,2
%A _Matthew Campbell_, Jun 29 2018
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