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

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.

Terms

    a(0) =0a(1) =1a(2) =1a(3) =9a(4) =77a(5) =1037a(6) =19113a(7) =464785a(8) =14410309a(9) =554826453a(10) =25971640865

External references