Number of subsets of {1,2,..n} that sum to 1 mod n.

Terms

a(0) =2a(1) =2a(2) =2a(3) =4a(4) =6a(5) =10a(6) =18a(7) =32a(8) =56a(9) =102a(10) =186a(11) =340a(12) =630a(13) =1170a(14) =2182a(15) =4096a(16) =7710a(17) =14560a(18) =27594a(19) =52428a(20) =99858a(21) =190650a(22) =364722a(23) =699040a(24) =1342176a(25) =2581110a(26) =4971008a(27) =9586980a(28) =18512790a(29) =35791358