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

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =3a(5) =4a(6) =6a(7) =14a(8) =28a(9) =49a(10) =95a(11) =196a(12) =386a(13) =754a(14) =1524a(15) =3102a(16) =6258a(17) =12700a(18) =26032a(19) =53440a(20) =109772a(21) =226457a(22) =468863a(23) =972300a(24) =2020274a(25) =4208530a(26) =8784556a(27) =18365322a(28) =38461110a(29) =80682740