Powers of 10: a(n) = 10^n.

Terms

a(0) =1a(1) =10a(2) =100a(3) =1000a(4) =10000a(5) =100000a(6) =1000000a(7) =10000000a(8) =100000000a(9) =1000000000a(10) =10000000000a(11) =100000000000a(12) =1000000000000