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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =17a(5) =51a(6) =161a(7) =519a(8) =1707a(9) =5711a(10) =19358a(11) =66342a(12) =229505a(13) =800333a(14) =2810370a(15) =9928806a(16) =35266403a(17) =125863071a(18) =451119566a(19) =1623142622a(20) =5860507205a(21) =21227095355a(22) =77108788287a(23) =280847802645