a(2*n+1) = 1, a(2*n) = 2*a(2*n-2) - 1.

Terms

a(0) =2a(1) =1a(2) =3a(3) =1a(4) =5a(5) =1a(6) =9a(7) =1a(8) =17a(9) =1a(10) =33a(11) =1a(12) =65a(13) =1a(14) =129a(15) =1a(16) =257a(17) =1a(18) =513a(19) =1a(20) =1025a(21) =1a(22) =2049a(23) =1a(24) =4097a(25) =1a(26) =8193a(27) =1a(28) =16385a(29) =1