A071606 - OEIS

%I #9 Jul 28 2024 19:44:23

%S 2,131,11311,1114111,111181111,11112721111,1111118111111,

%T 111111151111111,11111112521111111,1111111111111111111,

%U 111111111161111111111,11111111111111111111111,1111111111129211111111111,111111111111212111111111111,11111111111111611111111111111

%N Smallest zero-free palindromic prime of 2n + 1 digits.

%H Sean A. Irvine, <a href="/A071606/b071606.txt">Table of n, a(n) for n = 0..100</a>

%t a[n_] := Block[{k = (10^(n + 1) - 1)/9}, While[m = FromDigits[ Join[ IntegerDigits[k], Reverse[ Drop[ IntegerDigits[k], -1]]]]; !PrimeQ[m], k++ ]; m]; Table[ a[n], {n, 0, 13}]

%Y Cf. A028989.

%K nonn,base

%O 0,1

%A _Lekraj Beedassy_, Jun 21 2002

%E Edited by _Robert G. Wilson v_, Jun 21 2002

%E More terms from _Sean A. Irvine_, Jul 28 2024