This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A316297 #60 Apr 20 2024 23:58:11 %S A316297 1,4,36,288,7200,14400,705600,11289600,914457600,9144576000, %T A316297 1106493696000,13277924352000,2243969215488000,31415569016832000, %U A316297 471233535252480000,15079473128079360000,4357967734014935040000,26147806404089610240000,9439358111876349296640000 %N A316297 a(n) = n! times the denominator of the n-th harmonic number H(n). %F A316297 a(n) = A000142(n) * A002805(n). %e A316297 a(4) = 4! * A002805(4) = 24 * 12 = 288. %p A316297 H:= proc(n) H(n):= 1/n +`if`(n=1, 0, H(n-1)) end: %p A316297 a:= n-> denom(H(n))*n!: %p A316297 seq(a(n), n=1..20); # _Alois P. Heinz_, Jul 21 2018 %t A316297 a[n_] := n! Denominator@HarmonicNumber@n; Array[a, 18] (* _Robert G. Wilson v_, Jun 30 2018 *) %o A316297 (PARI) a(n) = n! * denominator(sum(k=1, n, 1/k)); \\ _Michel Marcus_, Aug 12 2018 %Y A316297 Cf. A000142, A001008, A002805, A027611, A027612, A124837, A124838. %K A316297 nonn %O A316297 1,2 %A A316297 _Matthew Campbell_, Jun 29 2018