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 A068687 #9 Jan 28 2023 12:10:38
%S A068687 313,353,373,383,3222223,3444443,322222223,355555553,3111111111113,
%T A068687 3444444444443,3888888888883,311111111111113,377777777777773,
%U A068687 3111111111111111111111111111113,3888888888888888888888888888883
%N A068687 Primes which are a sandwich of numbers made of only one digit between two 3's.
%C A068687 a(36) has 1065 digits. - _Michael S. Branicky_, Jan 28 2023
%H A068687 Michael S. Branicky, <a href="/A068687/b068687.txt">Table of n, a(n) for n = 1..35</a>
%o A068687 (Python)
%o A068687 from sympy import isprime
%o A068687 from itertools import count, islice
%o A068687 def agen(): yield from (t for i in count(1) for m in "124578" if isprime(t:=int("3" + m*i + "3")))
%o A068687 print(list(islice(agen(), 20))) # _Michael S. Branicky_, Jan 28 2023
%Y A068687 Cf. A068685.
%K A068687 base,nonn
%O A068687 1,1
%A A068687 _Amarnath Murthy_, Mar 02 2002
%E A068687 More terms from _Sascha Kurz_, Mar 17 2002