Binary reflected Gray code.

Terms

a(0) =0a(1) =1a(2) =11a(3) =10a(4) =110a(5) =111a(6) =101a(7) =100a(8) =1100a(9) =1101a(10) =1111a(11) =1110a(12) =1010a(13) =1011a(14) =1001a(15) =1000a(16) =11000a(17) =11001a(18) =11011a(19) =11010a(20) =11110a(21) =11111a(22) =11101a(23) =11100a(24) =10100a(25) =10101a(26) =10111a(27) =10110a(28) =10010a(29) =10011