G.f. A(x) satisfies: A(x)^3 = A( x^3/(1-3*x) ), with A(0) = 0.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =35a(6) =97a(7) =274a(8) =785a(9) =2275a(10) =6656a(11) =19630a(12) =58295a(13) =174175a(14) =523238a(15) =1579584a(16) =4789919a(17) =14584723a(18) =44577799a(19) =136732988a(20) =420784888a(21) =1298937282a(22) =4021383654a(23) =12483820395a(24) =38853994422a(25) =121220646116a(26) =379062880051