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

Terms

a(0) =0a(1) =1a(2) =0a(3) =0a(4) =0a(5) =0a(6) =2a(7) =0a(8) =0a(9) =5a(10) =2a(11) =0a(12) =0a(13) =13a(14) =43a(15) =0a(16) =0a(17) =193a(18) =274a(19) =0a(20) =0a(21) =1552a(22) =3245a(23) =0a(24) =0a(25) =18628a(26) =31048a(27) =0a(28) =0a(29) =188536