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
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.
Programs
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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