Number of solutions to +-1 +- 3 +- 6 +- ... +- n(n+1)/2 = 0.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =0a(6) =2a(7) =2a(8) =4a(9) =0a(10) =12a(11) =16a(12) =26a(13) =0a(14) =66a(15) =104a(16) =210a(17) =0a(18) =620a(19) =970a(20) =1748a(21) =0a(22) =5948a(23) =10480a(24) =18976a(25) =0a(26) =60836a(27) =111430a(28) =209460a(29) =0