18 in base 18-n.

Terms

a(0) =10a(1) =11a(2) =12a(3) =13a(4) =14a(5) =15a(6) =16a(7) =17a(8) =18a(9) =20a(10) =22a(11) =24a(12) =30a(13) =33a(14) =102a(15) =200a(16) =10010