a(n) = [x^(n*(n+1))] Sum_{m>=0} x^m * (x^(m+1) + i)^m / (1 + i*x^(m+1))^(m+1), for n >= 0.

Terms

a(0) =1a(1) =-2a(2) =-2a(3) =2a(4) =172a(5) =-2a(6) =-2a(7) =1372a(8) =2a(9) =-738612a(10) =-5332a(11) =7415020a(12) =2a(13) =-14644a(14) =-2a(15) =2a(16) =125777125816a(17) =-2a(18) =-2327347908a(19) =64012a(20) =2a(21) =-2a(23) =41693053276a(24) =2a(27) =2a(28) =292684a(31) =436924a(33) =-2a(34) =-628852a(38) =-2