

A087604


Smallest k such that n times concatenation of k with itself followed by a 3 is a prime, or 0 if no such number exists.


7



1, 1, 0, 1, 4, 0, 2, 1, 0, 1, 4, 0, 37, 7, 0, 17, 149, 0, 185, 7, 0, 73, 1, 0, 5, 47, 0, 38, 4, 0, 4, 133, 0, 52, 2, 0, 194, 46, 0, 37, 29, 0, 29, 25, 0, 19, 14, 0, 74, 8, 0, 19, 20, 0, 442, 83, 0, 358, 211, 0, 16, 298, 0, 260, 5, 0, 305, 71, 0, 8, 323, 0, 5, 109, 0, 8, 68, 0, 767, 367
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OFFSET

1,5


COMMENTS

Trivially a(3n) = 0. Conjecture: no other term is zero.
Either a(13)=0 or a(13)>36. This sequence contains no positive multiples of 3. If a(m) is of the form bbb...b (repeated k times) then a(km) <= b.  Sam Alexander, Oct 20 2003


LINKS

Table of n, a(n) for n=1..80.


EXAMPLE

a(5) = 4 as 444443 is a prime. but 111113,222223,333333 are not.


CROSSREFS

Cf. A086920, A087605, A087606, A087607, A087608, A087609, A087610.
Sequence in context: A019200 A324820 A337996 * A090538 A320157 A320479
Adjacent sequences: A087601 A087602 A087603 * A087605 A087606 A087607


KEYWORD

base,nonn


AUTHOR

Amarnath Murthy, Sep 18 2003


EXTENSIONS

More terms from Sam Alexander, Oct 20 2003
More terms from Ray G. Opao, Apr 15 2004
More terms from David Wasserman, Jun 16 2005


STATUS

approved



