Number of solutions to +- 1 +- 3 +- 5 +- 7 +- ... +- (4*n-3) = 1.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =5a(5) =13a(6) =38a(7) =118a(8) =380a(9) =1262a(10) =4277a(11) =14745a(12) =51541a(13) =182182a(14) =650095a(15) =2338706a(16) =8472697a(17) =30884150a(18) =113189168a(19) =416839177a(20) =1541726967a(21) =5724470097a(22) =21330062502a(23) =79733319862a(24) =298922247363