(( Primes == -1 (mod 4) ) + 1)/4.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =6a(5) =8a(6) =11a(7) =12a(8) =15a(9) =17a(10) =18a(11) =20a(12) =21a(13) =26a(14) =27a(15) =32a(16) =33a(17) =35a(18) =38a(19) =41a(20) =42a(21) =45a(22) =48a(23) =50a(24) =53a(25) =56a(26) =57a(27) =60a(28) =63a(29) =66