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A334735 Denominator of Sum_{k=1..n} k^2 / Product_{k=1..n} k^2. 3
1, 4, 18, 96, 2880, 518400, 181440, 135475200, 8778792960, 376233984000, 72425041920000, 4588850656051200, 47345284546560000, 217144413044342784000, 42750306318104985600000, 4974581098834034688000000, 70875936417673484697600000, 13663463022599094380003328000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(n) = denominator(n*(n + 1)*(2*n + 1)/6/(n!)^2).

EXAMPLE

The first few fractions are 1, 5/4, 7/18, 5/96, 11/2880, 91/518400, 1/181440, 17/135475200, 19/8778792960, ... = A125294/A334735.

MATHEMATICA

Table[Denominator[n*(n + 1)*(2*n + 1)/(6*(n!)^2)], {n, 1, 18}] (* Amiram Eldar, May 09 2020 *)

PROG

(PARI) a(n) = denominator(sum(k=1, n, k^2)/prod(k=1, n, k^2)); \\ Michel Marcus, May 09 2020

CROSSREFS

Cf. A125294 (numerators), A166602.

Sequence in context: A094304 A094258 A234854 * A086681 A054139 A020072

Adjacent sequences:  A334731 A334733 A334734 * A334736 A334737 A334738

KEYWORD

nonn,frac

AUTHOR

Petros Hadjicostas, May 09 2020

STATUS

approved

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Last modified August 10 14:50 EDT 2020. Contains 336381 sequences. (Running on oeis4.)