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A090648 a(n)=2*(4^n-1)/denominator(B(2n)) where B(k) denotes the k-th Bernoulli number. 1
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; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..28.

MATHEMATICA

Table[(2*(4^n-1))/Denominator[BernoulliB[2n]], {n, 0, 40}] (* Harvey P. Dale, Jul 20 2011 *)

PROG

(PARI) a(n)=2*(4^n-1)/denominator(bernfrac(2*n))

CROSSREFS

Cf. A001469.

Sequence in context: A188620 A152529 A126782 * A031024 A045437 A343413

Adjacent sequences:  A090645 A090646 A090647 * A090649 A090650 A090651

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Dec 13 2003

EXTENSIONS

Corrected and extended by Harvey P. Dale, Jul 20 2011

STATUS

approved

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Last modified September 28 06:57 EDT 2021. Contains 347703 sequences. (Running on oeis4.)