A020459 - OEIS

A020459

Primes that contain digits 2 and 7 only.

2, 7, 227, 277, 727, 2777, 7727, 22277, 22727, 22777, 27277, 72227, 72277, 72727, 272227, 272777, 727777, 777277, 2227727, 2227777, 2272727, 2277727, 2727727, 2772227, 7272227, 7722277, 7727777, 7772777, 7777727, 22227277, 22272277

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

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)

MATHEMATICA

Flatten[Table[Select[FromDigits/@Tuples[{2, 7}, n], PrimeQ], {n, 8}]] (* Vincenzo Librandi, Jul 27 2012 *)

PROG

(Magma) [p: p in PrimesUpTo(22272277) | Set(Intseq(p)) subset [2, 7]]; // Vincenzo Librandi, Jul 27 2012

CROSSREFS

Cf. A000040, A284921, A329760.

Sequence in context: A096463 A048560 A261267 * A343899 A088106 A343928

Adjacent sequences: A020456 A020457 A020458 * A020460 A020461 A020462

KEYWORD

nonn,base

AUTHOR

David W. Wilson

STATUS

approved