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A114363
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Denominator of zeta(4n)/zeta(2n)^2.
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1
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1, 5, 7, 715, 7293, 524875, 3547206349, 3393195750, 15419113345821, 26315472459271727875, 261083216622451556697, 2530298441183206558150, 39265828264113994596230058165, 61628134000978439089402342590
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| zeta(4n)/zeta(2n)^2 is a rational value expressible in term of Bernoulli's numbers (A027641).
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FORMULA
| Prod( (p^{2n}-1)/(p^{2n}+1) )=zeta(4n)/zeta(2n)^2 where the product is over all the primes.
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MATHEMATICA
| a[ n_] := If[ n < 0, 0, Denominator[ Zeta[4*n] / Zeta[2*n]^2 ]] (* Michael Somos, Jan 27 2012 *)
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PROG
| (PARI) z(n)=bernfrac(2*n)*(-1)^(n - 1)*2^(2*n-1)/(2*n)!; a(n)=if(n<1, 1, denominator(z(2*n)/z(n)^2))
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CROSSREFS
| Cf. A027641, A114362.
Sequence in context: A114368 A020467 A089344 * A083687 A101829 A056252
Adjacent sequences: A114360 A114361 A114362 * A114364 A114365 A114366
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KEYWORD
| frac,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 09 2006; corrected Feb 22 2006
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