Number of subsets of {1, 3, ..., 2*n-1} which sum to 0 modulo 2*n-1.

Terms

a(0) =2a(1) =2a(2) =2a(3) =2a(4) =4a(5) =6a(6) =10a(7) =18a(8) =30a(9) =54a(10) =98a(11) =178a(12) =328a(13) =608a(14) =1130a(15) =2114a(16) =3974a(17) =7490a(18) =14170a(19) =26890a(20) =51150a(21) =97542a(22) =186420a(23) =356962a(24) =684784a(25) =1315870a(26) =2532410a(27) =4880646a(28) =9418806a(29) =18199014