Dropping any digit gives 0, 1 or a composite number.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =6a(6) =7a(7) =8a(8) =9a(9) =10a(10) =11a(11) =14a(12) =16a(13) =18a(14) =19a(15) =40a(16) =41a(17) =44a(18) =46a(19) =48a(20) =49a(21) =60a(22) =61a(23) =64a(24) =66a(25) =68a(26) =69a(27) =80a(28) =81a(29) =84