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A288873 Numerators of scaled Bernoulli numbers 4^n*B(n), with B(n) = A027641(n)/A027642(n). 0
1, -2, 8, 0, -128, 0, 2048, 0, -32768, 0, 2621440, 0, -5796528128, 0, 939524096, 0, -7767448354816, 0, 1507258642989056, 0, -95993412418797568, 0, 7516375836686024704, 0, -33265288504730187726848, 0, 19259875741830735724544, 0, -855664510723636131971203072, 0, 4966694343692730467779807805440 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The denominators seem to be given in A141459.

See A285863 for comments on B(d;n) = d^n*B(n), for n >= 0, with e.g.f. d*x/(exp(d*x) - 1).

LINKS

Table of n, a(n) for n=0..30.

Wolfdieter Lang, On Sums of Powers of Arithmetic Progressions, and Generalized Stirling, Eulerian and Bernoulli numbers, arXiv:1707.04451 [math.NT], 2017.

FORMULA

a(n) = numerator(r(n)), with the rationals r(n) = 4^n*A027641(n)/A027642(n), n >= 0.

E.g.f. of {r(n)}_{n>=0}: 4*x/(exp(4*x) - 1).

EXAMPLE

The rationals r(n) begin: 1, -2, 8/3, 0, -128/15, 0, 2048/21, 0, -32768/15, 0, 2621440/33, 0, -5796528128/1365, 0, 939524096/3, 0, -7767448354816/255, 0, 1507258642989056/399, 0, -95993412418797568/165, ...

MAPLE

seq(numer(4^n*bernoulli(n)), n=0..28); # Peter Luschny, Jul 17 2017

MATHEMATICA

Table[4^n BernoulliB[n] // Numerator, {n, 0, 30}] (* Jean-Fran├žois Alcover, Jul 14 2018 *)

PROG

(PARI) a(n) = numerator(4^n*bernfrac(n)); \\ Michel Marcus, Jul 06 2017

(Python)

from sympy import bernoulli

def a(n): return (4**n * bernoulli(n)).numerator()

[a(n) for n in range(31)]  # Indranil Ghosh, Jul 06 2017

CROSSREFS

Cf. A141459, A027641/A027642, (-1)^n*A239275(n)/A141459(n) (B(2;n)), A285863/A285068 (B(3;n)).

Sequence in context: A021360 A028256 A209455 * A160636 A282626 A206712

Adjacent sequences:  A288870 A288871 A288872 * A288874 A288875 A288876

KEYWORD

sign,frac,easy

AUTHOR

Wolfdieter Lang, Jul 05 2017

STATUS

approved

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Last modified August 17 00:01 EDT 2022. Contains 356180 sequences. (Running on oeis4.)