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 A032684 #14 Apr 05 2020 13:33:50
%S A032684 2,5,8,9,12,17,18,20,23,24,29,30,41,45,47,48,50,51,53,54,57,60,68,71,
%T A032684 72,75,81,86,87,90,92,93,114,116,123,125,128,131,132,134,138,143,152,
%U A032684 153,159,164,170,177,180,183,186,188,191,194,198,204,207
%N A032684 Numbers k such that k surrounded by digit '7' is prime.
%H A032684 Daniel Starodubtsev, <a href="/A032684/b032684.txt">Table of n, a(n) for n = 1..10000</a>
%o A032684 (Python)
%o A032684 from sympy import isprime
%o A032684 print([i for i in range(200) if isprime(int('7' + str(i) + '7'))]) # _Daniel Starodubtsev_, Apr 05 2020
%Y A032684 Cf. A032689.
%K A032684 nonn,base
%O A032684 1,1
%A A032684 _Patrick De Geest_, May 15 1998