A277087 a(0) = 1, a(n) = (denominator of the Bernoulli number B_{2n})/3, for n>=1.

1, 2, 10, 14, 10, 22, 910, 2, 170, 266, 110, 46, 910, 2, 290, 4774, 170, 2, 639730, 2, 4510, 602, 230, 94, 15470, 22, 530, 266, 290, 118, 18928910, 2, 170, 21574, 10, 1562, 46700290, 2, 10, 1106, 76670, 166, 1134770, 2, 20470, 90706, 470, 2, 1500590, 2, 11110, 1442, 530, 214, 69730570, 506, 557090, 14, 590, 2, 776085310

Offset: 0

Author

Jonathan Sondow, Dec 12 2016

Keywords

• nonn
• frac

Comments

All terms except a(0) are odd multiples of 2, by the von Staudt-Clausen theorem. See A002445 and A027642 for comments, references, and links.

Links

• Robert Israel, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A001897, A002445, A027642.

Programs

Maple

1, seq(denom(bernoulli(2*n))/3,n=1..100); # Robert Israel, Dec 16 2016

Mathematica

Join[{1}, Denominator[BernoulliB[Range[2, 120, 2]]]/3]

PARI

a(n)=ceil(denominator(bernfrac(2*n))/3) \\ Charles R Greathouse IV, Dec 16 2016

Formula

a(0) = 1, a(n) = (1/3)*A002445(n) = (1/3)*A027642(2*n) = (2/3)*A001897(n) for n>0.