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 A020455 #41 Dec 09 2024 09:20:40
%S A020455 7,11,17,71,1117,1171,1777,7177,7717,11117,11171,11177,11717,11777,
%T A020455 17117,71171,71711,71777,77171,77711,1111711,1111771,1117111,1117117,
%U A020455 1117177,1171111,1171117,1171771,1177171,1177711,1177717,1711117,1717117,1771177,1771717
%N A020455 Primes that contain digits 1 and 7 only.
%C A020455 There are no terms whose number of digits is divisible by 3: for every d that is a multiple of 3, every d-digit number j consisting of no digits other than 1's and 7's will have a digit sum divisible by 3, so j will also be divisible by 3. - _Mikk Heidemaa_, Mar 26 2021
%H A020455 Alois P. Heinz, <a href="/A020455/b020455.txt">Table of n, a(n) for n = 1..20000</a> (first 1000 terms from Vincenzo Librandi)
%H A020455 James Maynard and Brady Haran, <a href="https://www.youtube.com/watch?v=eeoBCS7IEqs">Primes without a 7</a>, Numberphile video (2019)
%F A020455 { A000040 } intersect { A276039 }.
%t A020455 Flatten[Table[Select[FromDigits/@Tuples[{1,7},n],PrimeQ],{n,7}]] (* _Vincenzo Librandi_, Jul 27 2012 *)
%o A020455 (Magma) [p: p in PrimesUpTo(1771177) | Set(Intseq(p)) subset [1, 7]]; // _Vincenzo Librandi_, Jul 27 2012
%o A020455 (Python)
%o A020455 from sympy import isprime
%o A020455 def only17(n): return int(bin(n+1)[3:].replace('1', '7').replace('0', '1'))
%o A020455 def auptod(digs):
%o A020455 return list(filter(isprime, (only17(i) for i in range(1, 2**(digs+1)-1))))
%o A020455 print(auptod(8)) # _Michael S. Branicky_, Jul 11 2021
%Y A020455 Subsequence of A030096.
%Y A020455 Cf. A000040, A276039.
%K A020455 nonn,base
%O A020455 1,1
%A A020455 _David W. Wilson_