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A036946 Smallest n-digit prime containing only digits 5 and 7, or 0 if no such prime exists. 0
5, 0, 557, 5557, 57557, 555557, 5555777, 55555777, 555557557, 5555555557, 55555555777, 555555575557, 5555555757757, 55555555575757, 555555555555557, 5555555555557577, 55555555555777777, 555555555557557757, 5555555555555557577, 55555555555575755777 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

Flatten[Join[{5, 0}, Table[Select[FromDigits/@(Join[#, {7}]&/@Tuples[ {5, 7}, n]), PrimeQ, 1], {n, 2, 20}]]] (* Harvey P. Dale, Mar 08 2013 *)

CROSSREFS

Cf. A036229, A020467, A036320.

Sequence in context: A222327 A286483 A264884 * A027641 A164555 A176327

Adjacent sequences:  A036943 A036944 A036945 * A036947 A036948 A036949

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jan 04 1999.

EXTENSIONS

More terms from Harvey P. Dale, Mar 08 2013

STATUS

approved

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Last modified February 23 13:08 EST 2018. Contains 299581 sequences. (Running on oeis4.)