G.f. satisfies A(x) = f(x) + x*A(x)*f(x)^3, where f(x) = Sum_{k>=0} x^((4^k-1)/3).

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =36a(5) =96a(6) =254a(7) =676a(8) =1792a(9) =4756a(10) =12621a(11) =33490a(12) =88868a(13) =235818a(14) =625764a(15) =1660510a(16) =4406296a(17) =11692452a(18) =31026836a(19) =82332140a(20) =218474784a(21) =579739960a(22) =1538385398a(23) =4082226194a(24) =10832507040a(25) =28744906148a(26) =76276860598a(27) =202406625820