G.f. satisfies A(x) = 1/(1-x) + x^3*(1-x)*A(x)^4.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =7a(6) =15a(7) =36a(8) =82a(9) =191a(10) =471a(11) =1166a(12) =2884a(13) =7267a(14) =18523a(15) =47349a(16) =121821a(17) =315781a(18) =822165a(19) =2148811a(20) =5641035a(21) =14864295a(22) =39287907a(23) =104154066a(24) =276899112a(25) =737984583a(26) =1971375679a(27) =5277570860a(28) =14156881590a(29) =38045460023