G.f. satisfies A(x) = 1 + x*A(x)/(1 - x^3*A(x)^2).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =5a(6) =11a(7) =22a(8) =45a(9) =99a(10) =226a(11) =515a(12) =1168a(13) =2670a(14) =6186a(15) =14467a(16) =33985a(17) =80105a(18) =189636a(19) =451060a(20) =1077225a(21) =2580979a(22) =6201602a(23) =14942480a(24) =36098349a(25) =87417956a(26) =212159347a(27) =515937882a(28) =1257048536a(29) =3068146679