A187745 - OEIS

A187745

Numerators of Bernoulli numbers B(2^n).

1, 1, 1, -1, -1, -3617, -7709321041217, -106783830147866529886385444979142647942017

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,6

COMMENTS

Interestingly, the terms |a(n)| mod 100 show some regularity : 1, 1, 1, 1, 1, 17, 17, 17, 17, 69, 69, 69, 69, 69, 69, 69, 69, 53, 53, 53, 53, 53, ...

The only prime term up to a(20) is a(5)

LINKS

FORMULA

MATHEMATICA

A164555[n_] := If[n <= 2, 1, BernoulliB[n] // Numerator]; A131577[n_] := If[n == 0, 0, 2^(n-1)]; a[n_] := A164555[A131577[n]];

(* or *) a[n_] := n!*Coefficient[ Series[x/(1-Exp[-x]), {x, 0, 2^6}], x, Max[1, 2^(n-1)]] // Numerator; Table[a[n], {n, 0, 7}]

PROG

(Magma)

A164555:=func<n | n le 2 select 1 else Numerator(Bernoulli(n))>;

[A164555(2^(n-1)): n in [0..10]]; // Bruno Berselli, Jan 09 2013

CROSSREFS

KEYWORD

sign,frac

AUTHOR

STATUS

approved