A087536 Primes consisting only of digits 6 and 7 occurring with equal frequency.

67, 67766767, 76767667, 6666767777, 6667677677, 6667776767, 6667777667, 6676766777, 6676767677, 6676776677, 6677666777, 6677667767, 6677676767, 6766677767, 6766776677, 6767667677, 6767677667, 6776766677, 6776766767, 6776767667, 6777667667, 7666677677, 7666767677, 7667676677

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..5129 (first 5001 terms from Harvey P. Dale)

Crossrefs

Cf. A087510, A087511, A087535.

Programs

Mathematica

Sort[Flatten[Table[Select[FromDigits/@Permutations[PadRight[{},2n,{6,7}]],PrimeQ],{n,5}]]] (* Harvey P. Dale, Dec 03 2012 *)

PARI

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

Extensions

Edited by Charles R Greathouse IV, Oct 28 2009

Offset changed by Andrew Howroyd, Sep 20 2024