G.f.: A(x) = exp( Sum_{n>=1} x^n/n * (1 + x^n*A(x)^(2*n)) / (1 + x^n*A(x)^n) ).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =6a(6) =14a(7) =31a(8) =74a(9) =176a(10) =425a(11) =1055a(12) =2637a(13) =6671a(14) =16995a(15) =43507a(16) =112102a(17) =290347a(18) =755836a(19) =1976717a(20) =5189664a(21) =13673314a(22) =36139543a(23) =95795807a(24) =254610593a(25) =678385919a(26) =1811625931a(27) =4848177910a(28) =12999914523a(29) =34921821516