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