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

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =38a(6) =117a(7) =374a(8) =1226a(9) =4100a(10) =13932a(11) =47968a(12) =166976a(13) =586673a(14) =2077814a(15) =7410174a(16) =26588203a(17) =95913834a(18) =347655258a(19) =1265538557a(20) =4624629016a(21) =16958809018a(22) =62386998767a(23) =230172892750a(24) =851474002794