Binary numbers with 2 replacing 1 in odd positions.

Terms

a(0) =0a(1) =2a(2) =10a(3) =12a(4) =200a(5) =202a(6) =210a(7) =212a(8) =1000a(9) =1002a(10) =1010a(11) =1012a(12) =1200a(13) =1202a(14) =1210a(15) =1212a(16) =20000a(17) =20002a(18) =20010a(19) =20012a(20) =20200a(21) =20202a(22) =20210a(23) =20212a(24) =21000a(25) =21002a(26) =21010a(27) =21012a(28) =21200a(29) =21202