A087514 Primes consisting only of digits 1 and 7 occurring with equal frequency.

17, 71, 11171777, 11177717, 17111777, 17171177, 17171771, 17177117, 17711717, 17717171, 71117177, 71171717, 71717117, 77111717, 77711171, 1111717777, 1117117777, 1117177177, 1117771177, 1117771717, 1177117177, 1177177711

Offset

0,1

Comments

There are 18 digit pairs which can produce such primes. (1,0),(7,0),(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).

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Mathematica

Sort[Select[FromDigits/@Flatten[Table[Permutations[PadRight[{}, 2n, {1, 7}]], {n, 5}], 1], PrimeQ]] (* Harvey P. Dale, Jul 27 2019 *)

Crossrefs

Cf. A087510, A087515, A087516.

Sequence in context: A047978 A050524 A214530 * A119625 A130748 A131692

Adjacent sequences: A087511 A087512 A087513 * A087515 A087516 A087517

Keyword

base,nonn

Author

Amarnath Murthy and Paul D. Hanna, Sep 11 2003

Status

approved