G.f. satisfies: A(x) = x^2/(1-x) + A(A(x)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =14a(6) =36a(7) =85a(8) =226a(9) =577a(10) =1561a(11) =4158a(12) =11413a(13) =31200a(14) =86722a(15) =241227a(16) =677729a(17) =1908832a(18) =5411431a(19) =15386107a(20) =43949347a(21) =125896209a(22) =361904137a(23) =1043032250a(24) =3014490719a(25) =8732211825a(26) =25353395331a(27) =73759912892a(28) =215007439768a(29) =627844428958