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
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Crossrefs
Cf. A153770.
Programs
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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
Extensions
Extended by Ray Chandler, Jan 07 2009