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%I #11 May 09 2020 15:29:18
%S 1,4,18,96,2880,518400,181440,135475200,8778792960,376233984000,
%T 72425041920000,4588850656051200,47345284546560000,
%U 217144413044342784000,42750306318104985600000,4974581098834034688000000,70875936417673484697600000,13663463022599094380003328000000
%N Denominator of Sum_{k=1..n} k^2 / Product_{k=1..n} k^2.
%F a(n) = denominator(n*(n + 1)*(2*n + 1)/6/(n!)^2).
%e The first few fractions are 1, 5/4, 7/18, 5/96, 11/2880, 91/518400, 1/181440, 17/135475200, 19/8778792960, ... = A125294/A334735.
%t Table[Denominator[n*(n + 1)*(2*n + 1)/(6*(n!)^2)], {n, 1, 18}] (* _Amiram Eldar_, May 09 2020 *)
%o (PARI) a(n) = denominator(sum(k=1, n, k^2)/prod(k=1, n, k^2)); \\ _Michel Marcus_, May 09 2020
%Y Cf. A125294 (numerators), A166602.
%K nonn,frac
%O 1,2
%A _Petros Hadjicostas_, May 09 2020
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