a(2n+1) = |a(2n) - a(2n-1)|, a(2n) = a(n) + a(n-1), a(0) = -1.

Terms

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