Coefficient of x^n in (1 + x - n*x^2)^n.

Terms

a(0) =1a(1) =1a(2) =-3a(3) =-17a(4) =49a(5) =651a(6) =-1259a(7) =-38023a(8) =26433a(9) =2969299a(10) =2225101a(11) =-289389891a(12) =-692529551a(13) =33718183045a(14) =143578976997