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

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =4a(6) =7a(7) =12a(8) =25a(9) =55a(10) =115a(11) =245a(12) =564a(13) =1331a(14) =3103a(15) =7407a(16) =18388a(17) =46198a(18) =116503a(19) =299966a(20) =789426a(21) =2095941a(22) =5616114a(23) =15299205a(24) =42255533a(25) =117689096a(26) =331204936a(27) =944052610a(28) =2718150015a(29) =7891518587