%I
%S 11,13,29,43,49,71,103,109,127,131,143,173,181,217,223,229,239,241,
%T 251,259,263,287,301,307,311,341,353,367,377,383,403,407,419,433,449,
%U 473,481,493,503,509,523,547,553,559,577,599,617,619,623,643,689,691
%N Numbers k such that the string 1311k is the decimal expansion of a prime number.
%C 11 and 13 are twin primes.
%H Daniel Starodubtsev, <a href="/A107645/b107645.txt">Table of n, a(n) for n = 1..10000</a>
%e k=71: 131171 is prime.
%e k=131: 1311131 is prime.
%o (MAGMA) [ n: n in [1..800]  IsPrime(Seqint(Intseq(n) cat [1, 1, 3, 1])) ];
%K nonn,base
%O 1,1
%A _Parthasarathy Nambi_, Jun 09 2005
