A020454 Primes that contain digits 1 and 6 only.

11, 61, 661, 6661, 11161, 16111, 16661, 66161, 111611, 161611, 611111, 616111, 1111661, 1611161, 1616161, 1616611, 1661111, 1661161, 1666111, 6111661, 6116111, 6116161, 6161161, 6611611, 6661111, 6661661, 11111161, 11166611, 11616611

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Links

• Jason Bard, Table of n, a(n) for n = 1..10000 (First 1000 terms from Vincenzo Librandi)

Programs

Magma

[p: p in PrimesUpTo(11616611) | Set(Intseq(p)) subset [1, 6]]; // Vincenzo Librandi, Jul 27 2012. (see Berselli A020461).

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{1,6},n],PrimeQ],{n,8}]] (* Vincenzo Librandi, Jul 27 2012 *)
Select[Flatten[Table[10*FromDigits/@Tuples[{1,6},n]+1,{n,7}]],PrimeQ] (* Slightly faster than the above Mathematica program by forcing the last digit to be one. *) (* Harvey P. Dale, May 31 2018 *)