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A153771 Primes with a prime number of digits and using all of the prime digits 2, 3, 5, 7 repeated in strings, in that order. 3
23357, 23557, 2235557, 2335577, 2355557, 22222222357, 22222333577, 22223333357, 22223335577, 22223335777, 22223357777, 22233577777, 22333355777, 22335555577, 22355555557, 22355555777, 23333335577 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

F:= proc(d) local Res, x2, x3, x5, x7, x;

  Res:= NULL:

  for x2 from d-3 to 1 by -1 do

    for x3 from d-x2-2 to 1 by -1 do

      for x5 from d-x2-x3-1 to 1 by -1 do

        x7:= d-x2-x3-x5;

        x:= 7/9*(10^x7-1) + 5/9*(10^(x5+x7)-10^x7) + 3/9*(10^(x3+x5+x7)-10^(x5+x7)) + 2/9*(10^d-10^(x3+x5+x7));

        if isprime(x) then Res:= Res, x fi

  od od od:

  Res;

end proc:

seq(F(ithprime(i)), i=3..6); # Robert Israel, Feb 03 2019

CROSSREFS

Cf. A153770.

Sequence in context: A251111 A205834 A184229 * A252944 A246891 A189656

Adjacent sequences:  A153768 A153769 A153770 * A153772 A153773 A153774

KEYWORD

nonn,base

AUTHOR

Lekraj Beedassy, Jan 01 2009

EXTENSIONS

Extended by Ray Chandler, Jan 07 2009

STATUS

approved

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Last modified August 20 14:36 EDT 2019. Contains 326152 sequences. (Running on oeis4.)