Number of stacks of odd length in all 2ndary structures of size n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =6a(6) =16a(7) =44a(8) =113a(9) =290a(10) =749a(11) =1930a(12) =4966a(13) =12776a(14) =32870a(15) =84577a(16) =217665a(17) =560328a(18) =1442893a(19) =3716837a(20) =9577805a(21) =24689612a(22) =63667585a(23) =164239124a(24) =423824628a(25) =1094065998a(26) =2825169786a(27) =7297681867a(28) =18856458451a(29) =48737762624