A036318 -id:A036318

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A036944

Smallest n-digit prime containing only the digits 4 and 7, or 0 if no such prime exists.

+10
2

7, 47, 0, 4447, 44777, 0, 4444747, 44447747, 0, 4444444447, 44444444747, 0, 4444444447777, 44444447447447, 0, 4444444447447777, 44444444444444477, 0, 4444444444444444777, 44444444444444444447, 0, 4444444444444444444747, 44444444444444444444477, 0

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..500

MATHEMATICA

Flatten[Table[Select[FromDigits/@Tuples[{4, 7}, n], PrimeQ, 1], {n, 22}]/.{}->{0}] (* Harvey P. Dale, Jun 28 2012 *)

CROSSREFS

Cf. A036229, A020465, A036318.

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jan 04 1999

STATUS

approved

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