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A090648
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a(n)=2*(4^n-1)/denominator(B(2n)) where B(k) denotes the k-th Bernoulli number.
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0
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0, 1, 1, 3, 17, 31, 3, 5461, 257, 657, 6355, 60787, 12291, 22369621, 617093, 149943, 16843009, 5726623061, 71613, 91625968981, 162529435, 4870483401, 50991843607, 499069107643, 12129927891, 34118178995231, 5664905191661, 45148868444817, 165649641466501
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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MATHEMATICA
| Table[(2*(4^n-1))/Denominator[BernoulliB[2n]], {n, 0, 40}] (* From Harvey P. Dale, Jul 20 2011 *)
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PROG
| (PARI) a(n)=2*(4^n-1)/denominator(bernfrac(2*n))
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CROSSREFS
| Cf. A001469.
Sequence in context: A188620 A152529 A126782 * A031024 A045437 A115355
Adjacent sequences: A090645 A090646 A090647 * A090649 A090650 A090651
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 13 2003 Ben
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EXTENSIONS
| Corrected and extended by Harvey P. Dale, Jul 20 2011
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