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

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =1a(5) =0a(6) =1a(7) =1a(8) =2a(9) =2a(10) =3a(11) =3a(12) =4a(13) =5a(14) =7a(15) =9a(16) =12a(17) =15a(18) =19a(19) =24a(20) =31a(21) =40a(22) =53a(23) =68a(24) =88a(25) =113a(26) =145a(27) =186a(28) =241a(29) =311