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A106107 Primes with minimal digit = 7.

%I A106107 #6 Jan 07 2020 13:28:09
%S A106107 7,79,97,787,797,877,887,977,997,7789,7877,7879,8779,8887,9787,9887,
%T A106107 77797,77899,77977,77999,78779,78787,78797,78877,78887,78889,78977,
%U A106107 78979,78989,79777,79889,79979,79987,79997,79999
%N A106107 Primes with minimal digit = 7.
%H A106107 Robert Israel, <a href="/A106107/b106107.txt">Table of n, a(n) for n = 1..10000</a>
%p A106107 Res:= NULL:
%p A106107 count:= 0:
%p A106107 for d from 1 while count < 100 do
%p A106107   for m from 3^d to  2*3^d-1 while count < 100 do
%p A106107   L:= convert(m,base,3)[1..d];
%p A106107   if min(L) <> 0 then next fi;
%p A106107   x:= add((L[i]+7)*10^(i-1),i=1..d);
%p A106107   if isprime(x) then count:= count+1; Res:= Res, x; fi
%p A106107 od od:
%p A106107 Res; # _Robert Israel_, Jan 07 2020
%t A106107 Select[Prime[Range[8000]], Min[IntegerDigits[ # ]]==7&]
%K A106107 nonn,base
%O A106107 1,1
%A A106107 _Zak Seidov_, May 07 2005