A020457 Primes that contain digits 1 and 9 only.

11, 19, 191, 199, 911, 919, 991, 1999, 9199, 11119, 19919, 19991, 91199, 99119, 99191, 99991, 111119, 111191, 111919, 119191, 191119, 191911, 191999, 199999, 911111, 919111, 991999, 999199, 1111991, 1191119, 1191191, 1191199, 1191991, 1199999

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..20000 (first 1000 terms from Vincenzo Librandi)
• James Maynard and Brady Haran, Primes without a 7, Numberphile video (2019)

Crossrefs

Subsequence of A329761 and hence of A030096.

Programs

Magma

[p: p in PrimesUpTo(1199999) | Set(Intseq(p)) subset [1, 9]]; // Vincenzo Librandi, Jul 27 2012

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{1,9},n],PrimeQ],{n,7}]] (* Vincenzo Librandi, Jul 27 2012 *)