Bit to left of least significant 1-bit in binary expansion of n.

Terms

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