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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =7a(6) =14a(7) =31a(8) =67a(9) =146a(10) =331a(11) =760a(12) =1749a(13) =4072a(14) =9583a(15) =22673a(16) =53929a(17) =129055a(18) =310328a(19) =749152a(20) =1815481a(21) =4415313a(22) =10771564a(23) =26352955a(24) =64644926a(25) =158963191a(26) =391767016a(27) =967523138a(28) =2394060433a(29) =5934576763