a(n) = Sum_{d|n} phi(d)*10^(n/d).

Terms

a(0) =0a(1) =10a(2) =110a(3) =1020a(4) =10120a(5) =100040a(6) =1001220a(7) =10000060a(8) =100010240a(9) =1000002060a(10) =10000100440a(11) =100000000100