First odd semiprime > 10^n.

Terms

a(0) =9a(1) =15a(2) =111a(3) =1003a(4) =10001a(5) =100001a(6) =1000001a(7) =10000001a(8) =100000001a(9) =1000000013a(10) =10000000003a(11) =100000000007