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A087514 Primes consisting only of digits 1 and 7 occurring with equal frequency. 8
17, 71, 11171777, 11177717, 17111777, 17171177, 17171771, 17177117, 17711717, 17717171, 71117177, 71171717, 71717117, 77111717, 77711171, 1111717777, 1117117777, 1117177177, 1117771177, 1117771717, 1177117177, 1177177711 (list; graph; refs; listen; history; text; internal format)
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
MATHEMATICA
Sort[Select[FromDigits/@Flatten[Table[Permutations[PadRight[{}, 2n, {1, 7}]], {n, 5}], 1], PrimeQ]] (* Harvey P. Dale, Jul 27 2019 *)
CROSSREFS
Sequence in context: A047978 A050524 A214530 * A119625 A130748 A131692
KEYWORD
base,nonn
AUTHOR
STATUS
approved

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Last modified May 21 16:37 EDT 2024. Contains 372738 sequences. (Running on oeis4.)