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

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =24a(5) =60a(6) =148a(7) =370a(8) =920a(9) =2296a(10) =5720a(11) =14268a(12) =35568a(13) =88700a(14) =221156a(15) =551482a(16) =1375096a(17) =3428888a(18) =8549944a(19) =21319624a(20) =53160896a(21) =132558360a(22) =330537528a(23) =824204780a(24) =2055176304a(25) =5124638944a(26) =12778424976a(27) =31863351980a(28) =79452130896a(29) =198116051644