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