a(n) = a(n-1) + a(n - 1 minus the number of terms of a(k) == (mod 4) so far).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =7a(5) =11a(6) =14a(7) =25a(8) =36a(9) =50a(10) =64a(11) =89a(12) =125a(13) =175a(14) =225a(15) =314a(16) =378a(17) =467a(18) =592a(19) =817a(20) =992a(21) =1306a(22) =1684a(23) =2062a(24) =2529a(25) =2996a(26) =3988a(27) =4580a(28) =5572a(29) =6878