a(n) = n - floor(sqrt(n)) * ceiling(sqrt(n)).

Terms

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