Number of symmetric sum-free subsets of {1,2,...,n-1} with sums taken mod n.

Terms

a(0) =1a(1) =2a(2) =1a(3) =3a(4) =3a(5) =4a(6) =4a(7) =8a(8) =4a(9) =14a(10) =11a(11) =14a(12) =16a(13) =31a(14) =19a(15) =45a(16) =37a(17) =56a(18) =55a(19) =106a(20) =55a(21) =164a(22) =122a(23) =179a(24) =190a(25) =353a(26) =178a(27) =467a(28) =379a(29) =648