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

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =5a(5) =8a(6) =16a(7) =30a(8) =57a(9) =108a(10) =206a(11) =390a(12) =741a(13) =1407a(14) =2670a(15) =5068a(16) =9622a(17) =18262a(18) =34666a(19) =65806a(20) =124911a(21) =237109a(22) =450092a(23) =854368a(24) =1621784a(25) =3078519a(26) =5843709a(27) =11092672a(28) =21056400a(29) =39969753