A117626 - OEIS

%I #8 Jun 11 2015 06:51:08

%S 2,131,113,137,197,113,139,139,223,199,137,229,127,137,271,461,167,

%T 113,131,137,421,149,167,389,337,191,419,239,263,113,373,593,211,223,

%U 683,251,137,277,359,127,281,347,193,277,151,197,199,1321,337,1399,547,157

%N Least prime which stays prime when end digits (on both sides) are repeated n times.

%e We thus have successively the derived primes: 11311, 1111333, 111137777, 11111977777, 1111111333333, 111111139999999, ... .

%t f[n_] := Block[{k = 1}, While[id = IntegerDigits@ Prime@ k; !PrimeQ[ FromDigits@ Join[ Table[id[[1]], {n}], id, Table[id[[ -1]], {n}]]], k++ ]; Prime@k]; Table[ f@n, {n, 0, 51}] (* _Robert G. Wilson v_ *)

%K base,nonn

%O 0,1

%A _Lekraj Beedassy_, Apr 08 2006

%E More terms from _Robert G. Wilson v_, Apr 12 2006