a(n) = 10^n+5^n-1.

Terms

a(0) =1a(1) =14a(2) =124a(3) =1124a(4) =10624a(5) =103124a(6) =1015624a(7) =10078124a(8) =100390624a(9) =1001953124a(10) =10009765624a(11) =100048828124