A087537 Primes consisting only of digits 7 and 9 occurring with equal frequency.

79, 97, 77997979, 79779979, 79797997, 79997977, 99977797, 99979777, 7777997999, 7779799799, 7779799997, 7779979979, 7797799979, 7797979799, 7799797799, 7977799799, 7979799977, 7979979779, 7979979797, 7979979977, 7979997797, 7997799977, 7997979779, 7997997977

Offset: 1

Author

Amarnath Murthy and Paul D. Hanna, Sep 12 2003

Keywords

• base
• nonn

Comments

There are 18 digit pairs which can produce such primes. (1,0),(1,3),(1,4),(1,6),(1,7),(1,9),(2,3),(2,9),(3,4),(3,5),(3,7),(3,8),(4,7),(4,9),(5,9),(6,7),(7,9),(8,9).

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..9931

Crossrefs

Cf. A087510, A087511, A087536.

Programs

PARI

\\ Needs B() from A087510.
concat(vector(6,k,B(k,7,9,isprime))) \\ Andrew Howroyd, Sep 20 2024

Extensions

Edited by Charles R Greathouse IV, Oct 28 2009

Offset changed and a(22) onwards from Andrew Howroyd, Sep 20 2024