A106107 Primes with minimal digit = 7.

7, 79, 97, 787, 797, 877, 887, 977, 997, 7789, 7877, 7879, 8779, 8887, 9787, 9887, 77797, 77899, 77977, 77999, 78779, 78787, 78797, 78877, 78887, 78889, 78977, 78979, 78989, 79777, 79889, 79979, 79987, 79997, 79999

Offset: 1

Author

Zak Seidov, May 07 2005

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Programs

Maple

Res:= NULL:
count:= 0:
for d from 1 while count < 100 do
  for m from 3^d to  2*3^d-1 while count < 100 do
  L:= convert(m,base,3)[1..d];
  if min(L) <> 0 then next fi;
  x:= add((L[i]+7)*10^(i-1),i=1..d);
  if isprime(x) then count:= count+1; Res:= Res, x; fi
od od:
Res; # Robert Israel, Jan 07 2020

Mathematica

Select[Prime[Range[8000]], Min[IntegerDigits[ # ]]==7&]