G.f. A(x) satisfies A(x) = 1 / ((1 + x) * (1 - x * (1 + x + x^2 + x^3) * A(x^4))).

Terms

a(0) =1a(1) =0a(2) =2a(3) =2a(4) =6a(5) =9a(6) =20a(7) =36a(8) =72a(9) =138a(10) =269a(11) =520a(12) =1010a(13) =1958a(14) =3798a(15) =7365a(16) =14284a(17) =27704a(18) =53728a(19) =104202a(20) =202089a(21) =391939a(22) =760128a(23) =1474208a(24) =2859096a(25) =5544986a(26) =10754022a(27) =20856528a(28) =40449464a(29) =78448346