G.f. A(x) satisfies A(x) = 1 + x^3*A(x)^3*(1 + x*A(x)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =1a(5) =0a(6) =3a(7) =7a(8) =4a(9) =12a(10) =45a(11) =55a(12) =77a(13) =286a(14) =546a(15) =728a(16) =1960a(17) =4760a(18) =7548a(19) =15504a(20) =39729a(21) =75582a(22) =140448a(23) =336490a(24) =723327a(25) =1366200a(26) =2992990a(27) =6758895a(28) =13522275a(29) =28094040