a(n)=(number of digits <=2)-(number of digits >2) in base 5 representation of n.

Terms

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