Decimal expansion of 3^n contains no zeros (probably finite).

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =11a(11) =12a(12) =13a(13) =14a(14) =19a(15) =23a(16) =24a(17) =26a(18) =27a(19) =28a(20) =31a(21) =34a(22) =68