OFFSET
1,1
COMMENTS
B(2n) is negative for even n, but this does not affect the denominator. - M. F. Hasler, Dec 24 2013
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..500 (terms 1..50 from M. F. Hasler)
Ira Gessel, On Miki's identity for Bernoulli numbers J. Number Theory 110 (2005), no. 1, 75-82.
FORMULA
Miki's identity : B(n)*H(n)*(2/n) = sum(i=2, n-2, B(i)/i*B(n-i)/(n-i)*(1-C(n, i)))
MATHEMATICA
Denominator[Table[(BernoulliB[2n]HarmonicNumber[2n])/(n (-1)^(n+1)), {n, 20}]] (* Harvey P. Dale, Jun 25 2013 *)
PROG
(PARI) a(n)=denominator(bernfrac(2*n)*sum(k=1, 2*n, 1/k)/n)
(Python)
from sympy import bernoulli, harmonic
def a(n): return (bernoulli(2*n) * harmonic(2*n) / n).denominator()
print([a(n) for n in range(1, 22)]) # Indranil Ghosh, Aug 04 2017
CROSSREFS
Cf. A083687.
KEYWORD
frac,nonn
AUTHOR
Benoit Cloitre, Jun 15 2003
STATUS
approved