a(n)=(number of digits <=1)-(number of digits >1) in base 3 representation of n.

Terms

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