G.f. satisfies A(x) = Sum_{n>=0} x^(n*(n+1)/2) * A(x)^(n*(n+1)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =22a(5) =87a(6) =359a(7) =1535a(8) =6758a(9) =30431a(10) =139442a(11) =648001a(12) =3046730a(13) =14467286a(14) =69281190a(15) =334211603a(16) =1622568398a(17) =7921905397a(18) =38871120255a(19) =191586353683a(20) =948083155952