A111477 a(1) = 11, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

11, 19, 19, 37, 21, 71, 101, 39, 61, 87, 227, 63, 437, 153, 1363, 117, 363, 861, 609, 249, 23, 1077, 3123, 771, 3717, 633, 279, 1119, 927, 107, 3843, 4313, 1729, 627, 12541, 2403, 4083, 1239, 2227, 6441, 3819, 3983, 5631, 2303, 2971, 19217, 3633, 5109, 14413, 913

Offset: 1

Author

Amarnath Murthy, Aug 05 2005

Keywords

• base
• nonn

Examples

			11,111919,111919191919,... are all prime.
111919191919 = one copy of 11, two copies of 19, three copies of 19.
		

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111475, A111478.

Extensions

a(4)-a(8) from Stefan Steinerberger, Nov 17 2005

Extended by Max Alekseyev, May 20 2009