a(n) = 10*8^n+1.

Terms

a(0) =11a(1) =81a(2) =641a(3) =5121a(4) =40961a(5) =327681a(6) =2621441a(7) =20971521a(8) =167772161a(9) =1342177281a(10) =10737418241a(11) =85899345921a(12) =687194767361