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 A199347 #16 Jul 15 2025 10:49:41
%S A199347 3,7,37,43,47,73,337,347,373,433,443,733,743,773,3343,3347,3373,3433,
%T A199347 3733,4337,4373,4447,4733,7333,7433,7477,33343,33347,33377,33773,
%U A199347 34337,34747,37337,37447,37747,43777,44773,44777,47737,47743,47777,73433,73477,74377,74747,77347,77377,77447,77477,77743
%N A199347 Primes having only {3, 4, 7} as digits.
%H A199347 Harvey P. Dale, <a href="/A199347/b199347.txt">Table of n, a(n) for n = 1..10000</a>
%H A199347 <a href="/index/Pri#PrimesWithDigits">Index to entries for primes with digits in a given set</a>
%t A199347 Select[Flatten[Table[FromDigits/@Tuples[{3,4,7},n],{n,5}]],PrimeQ] (* _Harvey P. Dale_, Jul 31 2012 *)
%o A199347 (PARI) a(n, list=0, L=[3, 4, 7], reqpal=0)={my(t); for(d=1, 1e9, u=vector(d, i, 10^(d-i))~; forvec(v=vector(d, i, [1+(i==1&!L[1]), #L]), isprime(t=vector(d, i, L[v[i]])*u) || next; reqpal & !isprime(A004086(t)) & next; list & print1(t", "); n--||return(t)))}
%Y A199347 Cf. A020449 - A020472, A199325 - A199329.
%K A199347 nonn,base
%O A199347 1,1
%A A199347 _M. F. Hasler_, Nov 05 2011