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

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =0a(5) =0a(6) =4a(7) =7a(8) =0a(9) =0a(10) =35a(11) =62a(12) =0a(13) =0a(14) =361a(15) =657a(16) =0a(17) =0a(18) =4110a(19) =7636a(20) =0a(21) =0a(22) =49910a(23) =93846a(24) =0a(25) =0a(26) =632602a(27) =1199892a(28) =0a(29) =0