Expansion of g.f.: (1-2*x)/(1-3*x+2*x^3).

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =19a(5) =51a(6) =139a(7) =379a(8) =1035a(9) =2827a(10) =7723a(11) =21099a(12) =57643a(13) =157483a(14) =430251a(15) =1175467a(16) =3211435a(17) =8773803a(18) =23970475a(19) =65488555a(20) =178918059a(21) =488813227a(22) =1335462571a(23) =3648551595a(24) =9968028331a(25) =27233159851a(26) =74402376363a(27) =203271072427a(28) =555346897579