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

Terms

a(0) =2a(1) =2a(2) =4a(3) =4a(4) =8a(5) =12a(6) =20a(7) =32a(8) =60a(9) =104a(10) =188a(11) =344a(12) =632a(13) =1172a(14) =2192a(15) =4096a(16) =7712a(17) =14572a(18) =27596a(19) =52432a(20) =99880a(21) =190652a(22) =364724a(23) =699072a(24) =1342184a(25) =2581112a(26) =4971068a(27) =9586984a(28) =18512792a(29) =35791472