This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A069689 #6 Dec 05 2013 19:55:17
%S A069689 2,5,17,23,29,41,47,53,71,131,191,227,233,257,281,293,347,359,389,401,
%T A069689 419,431,479,503,521,557,593,599,653,659,677,683,701,761,797,827,857,
%U A069689 887,953,977,1091,1097,1109,1151,1181,1187,1193,1223,1283,1307,1373
%N A069689 Primes that yield another prime on placing a 7 on both sides (as leading and trailing digits).
%H A069689 Harvey P. Dale, <a href="/A069689/b069689.txt">Table of n, a(n) for n = 1..1000</a>
%e A069689 233 is a member as 72337 is also a prime.
%t A069689 Select[ Range[2000], PrimeQ[ # ] && PrimeQ[ FromDigits[ Insert[ IntegerDigits[ # ], 7, {{1}, {-1}}]]] &]
%t A069689 Select[Prime[Range[250]],PrimeQ[FromDigits[Join[{7}, IntegerDigits[ #],{7}]]]&] (* _Harvey P. Dale_, Nov 01 2011 *)
%Y A069689 Cf. A069687, A069688 & A069690.
%K A069689 nonn,base
%O A069689 1,1
%A A069689 _Amarnath Murthy_, Apr 06 2002
%E A069689 Edited and extended by _Robert G. Wilson v_, May 03 2002