G.f. satisfies: A(x) = 1 / Product_{n>=1} (1 + x^n*A(x)) * (1 + x^n/A(x)) * (1-x^n).

Terms

a(0) =1a(1) =-1a(2) =1a(3) =-3a(4) =6a(5) =-17a(6) =43a(7) =-125a(8) =348a(9) =-1029a(10) =3020a(11) =-9116a(12) =27567a(13) =-84620a(14) =260949a(15) =-812053a(16) =2539208a(17) =-7989121a(18) =25244540a(19) =-80136851a(20) =255325972a(21) =-816447638a(22) =2618870068a(23) =-8425244209a(24) =27176810469a(25) =-87879769383a(26) =284813417885a(27) =-925013053556