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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =17a(5) =51a(6) =161a(7) =524a(8) =1747a(9) =5939a(10) =20510a(11) =71756a(12) =253797a(13) =906032a(14) =3260380a(15) =11814305a(16) =43071858a(17) =157876851a(18) =581469125a(19) =2150809098a(20) =7986558110a(21) =29760593273a(22) =111252691988a(23) =417106577014