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.

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

Offset: 1

Author

Amarnath Murthy, Sep 18 2003

Keywords

• base
• nonn

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

Examples

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

Crossrefs

Cf. A086920, A087605, A087606, A087607, A087608, A087609, A087610.

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