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.

23357, 23557, 2235557, 2335577, 2355557, 22222222357, 22222333577, 22223333357, 22223335577, 22223335777, 22223357777, 22233577777, 22333355777, 22335555577, 22355555557, 22355555777, 23333335577

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