G.f. A(x) satisfies A(x^3)/A(x)^3 = 1 - 3*Sum_{n>=1} x^n/(1 + x^n + x^(2*n)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =17a(5) =49a(6) =146a(7) =444a(8) =1366a(9) =4243a(10) =13276a(11) =41818a(12) =132425a(13) =421186a(14) =1344724a(15) =4307464a(16) =13837365a(17) =44563750a(18) =143841132a(19) =465214791a(20) =1507319118a(21) =4891734608a(22) =15898701393a(23) =51742236543a(24) =168602613351a(25) =550016490269