G.f. satisfies A(x) = 1/(1-x) + x^2*A(x)^4.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =49a(6) =170a(7) =613a(8) =2275a(9) =8629a(10) =33301a(11) =130333a(12) =516077a(13) =2063685a(14) =8321892a(15) =33803161a(16) =138181521a(17) =568031297a(18) =2346668400a(19) =9737766513a(20) =40569611691a(21) =169632827345a(22) =711611670532