The number of irreducible zero-sum subsets of {-n..n} that contain -n but not n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =10a(6) =16a(7) =33a(8) =58a(9) =107a(10) =177a(11) =309a(12) =512a(13) =855a(14) =1396a(15) =2213a(16) =3464a(17) =5443a(18) =8311a(19) =12684a(20) =19149a(21) =28407a(22) =41965a(23) =61222a(24) =88912a(25) =126832a(26) =181455a(27) =254583a(28) =358776a(29) =497709