Write n in binary and replace 0 with 00.

Terms

a(0) =1a(1) =100a(2) =11a(3) =10000a(4) =1001a(5) =1100a(6) =111a(7) =1000000a(8) =100001a(9) =100100a(10) =10011a(11) =110000a(12) =11001a(13) =11100a(14) =1111a(15) =100000000a(16) =10000001a(17) =10000100a(18) =1000011a(19) =10010000a(20) =1001001a(21) =1001100a(22) =100111a(23) =11000000a(24) =1100001a(25) =1100100a(26) =110011a(27) =1110000