G.f. is the imaginary part of the function C(x) that satisfies: C(x) = 1 + x/C(I*x).

Terms

a(0) =-1a(1) =-1a(2) =0a(3) =1a(4) =2a(5) =2a(6) =0a(7) =-3a(8) =-6a(9) =-6a(10) =0a(11) =10a(12) =20a(13) =20a(14) =0a(15) =-35a(16) =-70a(17) =-70a(18) =0a(19) =126a(20) =252a(21) =252a(22) =0a(23) =-462a(24) =-924a(25) =-924a(26) =0a(27) =1716a(28) =3432a(29) =3432