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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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1
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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
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OFFSET
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0,4
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LINKS
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MATHEMATICA
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Table[(2*(4^n-1))/Denominator[BernoulliB[2n]], {n, 0, 40}] (* Harvey P. Dale, Jul 20 2011 *)
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PROG
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(PARI) a(n)=2*(4^n-1)/denominator(bernfrac(2*n))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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