G.f. A(x) satisfies A(x) = 1 + x^4*(1+x)*A(x)^4.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =1a(5) =1a(6) =0a(7) =0a(8) =4a(9) =8a(10) =4a(11) =0a(12) =22a(13) =66a(14) =66a(15) =22a(16) =140a(17) =560a(18) =840a(19) =560a(20) =1109a(21) =4845a(22) =9690a(23) =9690a(24) =11929a(25) =43473a(26) =106260a(27) =141680a(28) =160080a(29) =419244