A124131 a(n)=((-1)^n/2)*sum_{i1+i2+i3=2n} ((2*n)!/(i1! i2! i3!))*B(i1+i2) where B are the Bernoulli numbers.

0, 1, 1, 9, 77, 1037, 19113, 464785, 14410309, 554826453, 25971640865, 1452575521241, 95664836241981, 7327813077384349, 645942544224008857, 64924081840553650977, 7380723366892082000693, 942257770864409337556325

Offset

1,4

Links

Table of n, a(n) for n=1..18.

Formula

a(n) =(-1)^(n+1)*(B(2n)*(4^n-1)-1/2)

Prog

(PARI) a(n)=(-1)^(n+1)*(bernfrac(2*n)*(4^n-1)-1/2)

Crossrefs

Cf. A001469.

Sequence in context: A346847 A355372 A046150 * A000445 A046196 A231596

Adjacent sequences: A124128 A124129 A124130 * A124132 A124133 A124134

Keyword

nonn

Author

Benoit Cloitre, Nov 30 2006

Status

approved