A086920 Smallest k such that n times concatenation of k with itself followed by a 1 is a prime, or 0 if no such number exists.

1, 3, 2, 3, 3, 3, 3, 30, 6, 4, 5, 5, 25, 42, 17, 19, 2, 1, 7, 6, 6, 1, 50, 29, 138, 153, 4, 45, 54, 7, 15, 9, 78, 147, 95, 58, 102, 18, 3, 115, 54, 6, 46, 9, 24, 64, 183, 120, 3, 33, 112, 46, 105, 4, 279, 122, 68, 75, 3, 22, 294, 56, 92, 76, 6, 19, 94, 71, 12, 75, 30, 16, 78, 320, 33

Offset: 1

Author

Amarnath Murthy, Sep 18 2003

Keywords

• base
• nonn

Comments

Conjecture: no term is zero.

Examples

			a(3) = 2 as 2221 is a prime. a(4) = 3 as 33331 is a prime but 11111 and 22221 are not.
a(8) = 30 and the prime arising is 30303030303030301.
		

Crossrefs

Cf. A087604, A087605, A087606, A087607, A087608, A087609.

Cf. A086923.

Cf. A086766.

Extensions

More terms from Ray G. Opao, Apr 15 2004

More terms from David Wasserman, Apr 12 2005