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

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =7a(5) =12a(6) =19a(7) =31a(8) =52a(9) =86a(10) =141a(11) =233a(12) =386a(13) =639a(14) =1057a(15) =1749a(16) =2896a(17) =4795a(18) =7937a(19) =13138a(20) =21751a(21) =36010a(22) =59613a(23) =98688a(24) =163380a(25) =270479a(26) =447779a(27) =741300a(28) =1227231a(29) =2031697