A105437 Smallest prime that remains prime when a string of n 1's is prepended to it.

2, 3, 3, 7, 3, 83, 31, 7, 3, 29, 3, 53, 23, 439, 23, 53, 31, 71, 31, 79, 89, 233, 7, 3, 227, 487, 281, 31, 7, 227, 47, 439, 29, 47, 349, 491, 43, 31, 23, 7, 919, 701, 229, 283, 281, 59, 223, 2693, 53, 67, 239, 2011, 2113, 467, 41, 601, 587, 311, 337, 2879, 59, 619, 71

Offset: 0

Author

Lekraj Beedassy, Apr 08 2005

Keywords

• nonn
• base

Examples

			a(3)=7 because it is the first prime before 31,59,61,71,73,97,... all remaining prime when 111 is prepended to each of them.
		

Crossrefs

Cf. A105436, A065584.

Programs

Mathematica

f[n_] := Block[{k = 1, t = Table[1, {n}]}, While[id = IntegerDigits[ Prime[k]]; id[[1]] == 1 || !PrimeQ[ FromDigits[ Join[t, id]]], k++ ]; Prime[k]]; Table[ f[n], {n, 0, 62}] (* Robert G. Wilson v, Apr 09 2005 *)

Extensions

More terms from Robert G. Wilson v, Apr 09 2005