a(n) is the concatenation of n and 3n in binary.

Terms

a(0) =0a(1) =7a(2) =22a(3) =57a(4) =76a(5) =95a(6) =210a(7) =245a(8) =280a(9) =315a(10) =350a(11) =737a(12) =804a(13) =871a(14) =938a(15) =1005a(16) =1072a(17) =1139a(18) =1206a(19) =1273a(20) =1340a(21) =1407a(22) =2882a(23) =3013a(24) =3144a(25) =3275a(26) =3406a(27) =3537a(28) =3668a(29) =3799