Number of distinct primes == 1 (mod 4) dividing n.

Terms

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