a(n) is the number of occurrences of '11' in the binary expansion of n.

Terms

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