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A334735
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Denominator of Sum_{k=1..n} k^2 / Product_{k=1..n} k^2.
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3
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1, 4, 18, 96, 2880, 518400, 181440, 135475200, 8778792960, 376233984000, 72425041920000, 4588850656051200, 47345284546560000, 217144413044342784000, 42750306318104985600000, 4974581098834034688000000, 70875936417673484697600000, 13663463022599094380003328000000
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = denominator(n*(n + 1)*(2*n + 1)/6/(n!)^2).
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EXAMPLE
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The first few fractions are 1, 5/4, 7/18, 5/96, 11/2880, 91/518400, 1/181440, 17/135475200, 19/8778792960, ... = A125294/A334735.
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MATHEMATICA
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Table[Denominator[n*(n + 1)*(2*n + 1)/(6*(n!)^2)], {n, 1, 18}] (* Amiram Eldar, May 09 2020 *)
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PROG
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(PARI) a(n) = denominator(sum(k=1, n, k^2)/prod(k=1, n, k^2)); \\ Michel Marcus, May 09 2020
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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