G.f.: (1+x^3)/(1-x-x^6).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =2a(6) =3a(7) =4a(8) =5a(9) =7a(10) =9a(11) =11a(12) =14a(13) =18a(14) =23a(15) =30a(16) =39a(17) =50a(18) =64a(19) =82a(20) =105a(21) =135a(22) =174a(23) =224a(24) =288a(25) =370a(26) =475a(27) =610a(28) =784a(29) =1008