A124135 a(n)=((-1)^n/6)*sum_{i1+i2+i3+i4=2n} ((2*n)!/(i1! i2! i3! i4!))*B(i1+i2+i3) where B are the Bernoulli numbers.

0, 0, 3, 46, 1041, 32592, 1375919, 75858738, 5309829837, 460680712084, 48552875077995, 6111752613274230, 905772678574995593, 156116663818415074776, 30964395850928510817831

Offset

1,3

Links

Table of n, a(n) for n=1..15.

Formula

a(n)=(-1)^(n+1)*{ (9^n/4-4^n+3/4)*B(2n)+1/6}

Prog

(PARI) a(n)=(-1)^(n+1)*((9^n/4-4^n+3/4)*bernfrac(2*n)+1/6)

Crossrefs

Sequence in context: A278621 A231789 A119401 * A307292 A307290 A193420

Adjacent sequences: A124132 A124133 A124134 * A124136 A124137 A124138

Keyword

nonn

Author

Benoit Cloitre, Nov 30 2006

Status

approved