G.f. satisfies A(x) = 1 + x + 2*x^3*A(x)^3.

Terms

a(0) =1a(1) =1a(2) =0a(3) =2a(4) =6a(5) =6a(6) =14a(7) =60a(8) =120a(9) =216a(10) =732a(11) =2028a(12) =4240a(13) =11280a(14) =33696a(15) =83328a(16) =207072a(17) =591360a(18) =1606752a(19) =4102656a(20) =11172528a(21) =31167280a(22) =83112000a(23) =223249824a(24) =619860960a(25) =1699634784a(26) =4603619616a(27) =12689107200a(28) =35170240512a(29) =96523315200