Expansion of g/(1 - x^3*g), where g = 1+x*g^2 is the g.f. of A000108.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =16a(5) =47a(6) =147a(7) =474a(8) =1571a(9) =5320a(10) =18320a(11) =63959a(12) =225858a(13) =805288a(14) =2894978a(15) =10481813a(16) =38188689a(17) =139900745a(18) =515022101a(19) =1904268957a(20) =7068660708a(21) =26332347288a(22) =98411323603a(23) =368876938837