Number of solutions to 1 +- 2 +- 3 +- ... +- n == 0 (mod n).

Terms

a(0) =1a(1) =0a(2) =2a(3) =4a(4) =4a(5) =0a(6) =10a(7) =32a(8) =30a(9) =0a(10) =94a(11) =344a(12) =316a(13) =0a(14) =1096a(15) =4096a(16) =3856a(17) =0a(18) =13798a(19) =52432a(20) =49940a(21) =0a(22) =182362a(23) =699072a(24) =671092a(25) =0a(26) =2485534a(27) =9586984a(28) =9256396a(29) =0