G.f. A(x) satisfies 1/x = Sum_{n=-oo..+oo} A(x)^n * (A(x)^n - 1)^(n+1).

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =4a(5) =9a(6) =45a(7) =164a(8) =546a(9) =1493a(10) =3944a(11) =10588a(12) =32997a(13) =112945a(14) =396404a(15) =1330461a(16) =4265180a(17) =13292275a(18) =41778612a(19) =135378928a(20) =452828655a(21) =1534394542a(22) =5175561385a(23) =17246318586a(24) =56998526633a(25) =188492707958a(26) =628391304843