login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 18 04:44 EST 2019. Contains 329248 sequences. (Running on oeis4.)