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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =15a(6) =30a(7) =66a(8) =154a(9) =352a(10) =800a(11) =1864a(12) =4415a(13) =10474a(14) =24935a(15) =59845a(16) =144527a(17) =350271a(18) =852002a(19) =2080955a(20) =5100468a(21) =12537191a(22) =30900833a(23) =76363218a(24) =189162367a(25) =469590870a(26) =1168098275a(27) =2911137073a(28) =7267923924a(29) =18174761288