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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =7a(5) =21a(6) =54a(7) =141a(8) =407a(9) =1231a(10) =3691a(11) =10990a(12) =33144a(13) =101674a(14) =314679a(15) =977289a(16) =3047527a(17) =9557503a(18) =30133759a(19) =95390622a(20) =302960929a(21) =965282651a(22) =3085146472a(23) =9888455045a(24) =31774215928a(25) =102334358736a(26) =330298415136