A036944 Smallest n-digit prime containing only the digits 4 and 7, or 0 if no such prime exists.
7, 47, 0, 4447, 44777, 0, 4444747, 44447747, 0, 4444444447, 44444444747, 0, 4444444447777, 44444447447447, 0, 4444444447447777, 44444444444444477, 0, 4444444444444444777, 44444444444444444447, 0, 4444444444444444444747, 44444444444444444444477, 0
Offset: 1
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..500
Programs
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Mathematica
Flatten[Table[Select[FromDigits/@Tuples[{4,7},n],PrimeQ,1],{n,22}]/.{}->{0}] (* Harvey P. Dale, Jun 28 2012 *)