Alternate digits 1 and 0.

Terms

a(0) =0a(1) =1a(2) =10a(3) =101a(4) =1010a(5) =10101a(6) =101010a(7) =1010101a(8) =10101010a(9) =101010101a(10) =1010101010a(11) =10101010101a(12) =101010101010