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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =8a(7) =15a(8) =26a(9) =46a(10) =81a(11) =149a(12) =272a(13) =499a(14) =916a(15) =1701a(16) =3168a(17) =5921a(18) =11095a(19) =20880a(20) =39407a(21) =74558a(22) =141386a(23) =268776a(24) =512059a(25) =977419a(26) =1869033a(27) =3580161a(28) =6868969a(29) =13198565