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%I #14 Apr 18 2014 04:09:45
%S 3,7,37,73,337,373,733,773,3373,3733,7333,33377,33773,37337,77377,
%T 77773,333337,333737,373777,377737,733333,733373,737773,773777,777373,
%U 777737,3333373,3333773,3337333,3337777,3377377,3733333,3773377,3773773,3777377
%N Primes that contain digits 3 and 7 only.
%H Vincenzo Librandi, <a href="/A020463/b020463.txt">Table of n, a(n) for n = 1..1000</a>
%H MathOverflow, <a href="http://mathoverflow.net/questions/117689">3-7 primes in base 10</a>
%t Flatten[Table[Select[FromDigits/@Tuples[{3,7},n],PrimeQ],{n,7}]] (* _Vincenzo Librandi_, Jul 27 2012 *)
%Y A143967, A020458. [From _Reinhard Zumkeller_, Sep 06 2008]
%K nonn,base
%O 1,1
%A _David W. Wilson_
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