Double-bitters: only even length runs in binary expansion.

Terms

a(0) =0a(1) =3a(2) =12a(3) =15a(4) =48a(5) =51a(6) =60a(7) =63a(8) =192a(9) =195a(10) =204a(11) =207a(12) =240a(13) =243a(14) =252a(15) =255a(16) =768a(17) =771a(18) =780a(19) =783a(20) =816a(21) =819a(22) =828a(23) =831a(24) =960a(25) =963a(26) =972a(27) =975a(28) =1008a(29) =1011