Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #10 Sep 01 2013 13:46:07
%S 110311,110711,111211,111611,112111,113011,113111,114311,115211,
%T 115811,116411,116911,117511,117811,117911,118211,118411,119311,
%U 119611,130513,131113,131213,131413,131713,132113,132313,133013,133213,133813,134213,134513,135613
%N Primes of the form abcdabcd..abcdab.
%C The sequence appears to be infinite. The number of terms below 10^1000 are 5211.
%H Shyam Sunder Gupta, <a href="/A187114/b187114.txt">Table of n, a(n) for n = 1..2711</a>
%e a(2)= 110711 is in the sequence because it is a prime of the form abcdab.
%t s[n_]:=Select[Union@Flatten@Table[FromDigits@Flatten@Join[IntegerDigits@Table[b, {n}], {IntegerDigits@Floor[b/100]}], {b, 1000, 9999}], PrimeQ]; Array[s, 2]//Flatten
%Y Cf. A228625, A228627
%K nonn,base
%O 1,1
%A _Shyam Sunder Gupta_, Aug 30 2013