G.f. satisfies: A(x) = Sum_{n>=0} x^n * Sum_{k=0..n} x^k * {[x^k] A(x)^(2*n)}.

Terms

a(0) =1a(1) =1a(2) =3a(3) =5a(4) =25a(5) =42a(6) =203a(7) =352a(8) =1863a(9) =3221a(10) =17028a(11) =29700a(12) =160011a(13) =279869a(14) =1515002a(15) =2660203a(16) =14496687a(17) =25519004a(18) =139589213a(19) =246299404a(20) =1351864004a(21) =2389786433a(22) =13150095286a(23) =23284570446a(24) =128400299029a(25) =227675571607