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

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =37a(5) =93a(6) =229a(7) =563a(8) =1391a(9) =3439a(10) =8493a(11) =20973a(12) =51805a(13) =127975a(14) =316123a(15) =780867a(16) =1928877a(17) =4764693a(18) =11769661a(19) =29073159a(20) =71815939a(21) =177398387a(22) =438206105a(23) =1082448217a(24) =2673842665a(25) =6604874695a(26) =16315234267a(27) =40301577123a(28) =99552178897a(29) =245911873753