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 A102500 #7 Mar 14 2015 16:58:38
%S A102500 15,18,19,34,36,39,48,52,57,60,67,75,79,81,85,96,97,1005,1020,1030,
%T A102500 1047,1054,1062,1065,1074,1084,1086,1090,1096,1108,1128,1152,1153,
%U A102500 1164,1171,1173,1179,1182,1185,1189,1213,1215,1219,1228,1231,1233,1257,1269,1279
%N A102500 Values of n for which the concatenation 7nn7 (from sequence A100897) are primes.
%e A102500 The number 715157 is prime and corresponds to n=15.
%e A102500 The number 7100510057 is prime and corresponds to n=1005.
%t A102500 fQ[n_] := Block[{id = IntegerDigits[n]}, PrimeQ[ FromDigits[ Join[{7}, id, id, {7}]]]]; Select[ Range[1290], fQ[ # ] &] (* _Robert G. Wilson v_, Jan 14 2004 *)
%Y A102500 The full sequence of integers of the form 7nn7 is A100897. The primes that correspond to these values of n are sequence A102501.
%K A102500 easy,nonn,base
%O A102500 1,1
%A A102500 Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005
%E A102500 More terms from _Robert G. Wilson v_, Jan 14 2005