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

Terms

a(0) =1a(1) =0a(2) =0a(3) =2a(4) =2a(5) =0a(6) =0a(7) =8a(8) =14a(9) =0a(10) =0a(11) =70a(12) =124a(13) =0a(14) =0a(15) =722a(16) =1314a(17) =0a(18) =0a(19) =8220a(20) =15272a(21) =0a(22) =0a(23) =99820a(24) =187692a(25) =0a(26) =0a(27) =1265204a(28) =2399784a(29) =0