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 A036937 #20 Nov 07 2021 19:02:08
%S A036937 2,23,223,2333,23333,222323,2222333,22222223,222323333,2222232323,
%T A036937 22222222223,222222333323,2222222222323,22222222223323,
%U A036937 222222222332233,2222222222323223,22222222222233323,222222222222233323,2222222222222233333,22222222222222232233
%N A036937 Smallest n-digit prime containing only digits 2 and 3.
%C A036937 It is conjectured that such a prime exists for every value of n.
%H A036937 Alois P. Heinz, <a href="/A036937/b036937.txt">Table of n, a(n) for n = 1..400</a>
%H A036937 Robert G. Wilson v, <a href="/A069841/a069841.txt">Comments and first 121 terms</a>
%t A036937 Do[p = 2(10^n - 1)/9; k = 0; While[ ! PrimeQ[p], k++; p = FromDigits[ PadLeft[ IntegerDigits[k, 2], n] + 2]]; Print[p], {n, 1, 30}] (* _Robert G. Wilson v_, Apr 20 2002 *)
%t A036937 Table[SelectFirst[FromDigits/@Tuples[{2,3},n],PrimeQ],{n,20}] (* _Harvey P. Dale_, Nov 07 2021 *)
%o A036937 (Python)
%o A036937 from sympy import isprime
%o A036937 from itertools import product
%o A036937 def a(n):
%o A036937 for b in product("01", repeat=n):
%o A036937 m = int("".join(b).replace("0", "2").replace("1", "3"))
%o A036937 if isprime(m): return m
%o A036937 return None
%o A036937 print([a(n) for n in range(1, 21)]) # _Michael S. Branicky_, Feb 23 2021 after _Robert G. Wilson v_
%Y A036937 Cf. A036229, A020458, A036310, A069841.
%K A036937 nonn,base
%O A036937 1,1
%A A036937 _Patrick De Geest_, Jan 04 1999
%E A036937 Edited by _Jon E. Schoenfield_, Mar 27 2014