OFFSET
0,2
COMMENTS
Numerator is (-1)^(n+1)*A046990(n).
LINKS
Michel Marcus, Table of n, a(n) for n = 0..100
William Rowan Hamilton, On an expression for the numbers of Bernoulli, by means of a definite integral, and on some connected processes of summation and integration, Philosophical Magazine, 23 (1843), pp. 360-367.
FORMULA
a(n) = denominator of (1/Pi)*Integral(x>=0, (sin(x)/x)^(2*n)*sin(2*n*x)*tan(x)).
MATHEMATICA
a[n_] := Denominator[4^n (4^n-1)/2 BernoulliB[2n]/(2n)!];
Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Jun 18 2019 *)
PROG
(PARI) a(n) = denominator((4^n*(4^n-1)/2)*bernfrac(2*n)/(2*n)!); \\ Michel Marcus, Jun 18 2019
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Peter Luschny, Apr 05 2012
STATUS
approved