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A020459 Primes that contain digits 2 and 7 only. 7

%I

%S 2,7,227,277,727,2777,7727,22277,22727,22777,27277,72227,72277,72727,

%T 272227,272777,727777,777277,2227727,2227777,2272727,2277727,2727727,

%U 2772227,7272227,7722277,7727777,7772777,7777727,22227277,22272277

%N Primes that contain digits 2 and 7 only.

%H Alois P. Heinz, <a href="/A020459/b020459.txt">Table of n, a(n) for n = 1..20000</a> (first 1000 terms from Vincenzo Librandi)

%H James Maynard and Brady Haran, <a href="https://www.youtube.com/watch?v=eeoBCS7IEqs">Primes without a 7</a>, Numberphile video (2019)

%t Flatten[Table[Select[FromDigits/@Tuples[{2,7},n],PrimeQ],{n,8}]] (* _Vincenzo Librandi_, Jul 27 2012 *)

%o (MAGMA) [p: p in PrimesUpTo(22272277) | Set(Intseq(p)) subset [2, 7]]; // _Vincenzo Librandi_, Jul 27 2012

%Y Cf. A000040, A284921, A329760.

%K nonn,base

%O 1,1

%A _David W. Wilson_

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Last modified August 8 23:02 EDT 2020. Contains 336300 sequences. (Running on oeis4.)