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A020471 Primes that contain digits 7 and 9 only. 11
7, 79, 97, 797, 977, 997, 77797, 77977, 77999, 79777, 79979, 79997, 79999, 97777, 777977, 777979, 779797, 797977, 799979, 799999, 999979, 7777997, 7779979, 7779997, 7797799, 7797997, 7799797, 7799999, 7977779, 7977797, 7977799, 7977997 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index to entries about primes with digits in a given set

MATHEMATICA

Flatten[Table[Select[FromDigits/@Tuples[{7, 9}, n], PrimeQ], {n, 7}]] (* Vincenzo Librandi, Jul 28 2012 *)

PROG

(MAGMA) [p: p in PrimesUpTo(7977997) | Set(Intseq(p)) subset [7, 9]]; // Vincenzo Librandi, Jul 28 2012

CROSSREFS

Cf. A020449 (digits 0 & 1), ..., A020472 (digits 8 & 9).

Sequence in context: A082992 A261181 A106107 * A065902 A140613 A139945

Adjacent sequences:  A020468 A020469 A020470 * A020472 A020473 A020474

KEYWORD

nonn,base,changed

AUTHOR

David W. Wilson

EXTENSIONS

Edited by M. F. Hasler, Jul 26 2015

STATUS

approved

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Last modified October 23 21:16 EDT 2018. Contains 316541 sequences. (Running on oeis4.)