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 A087534 #14 Sep 20 2024 23:54:40
%S A087534 44994949,49444999,49494499,49499449,94449499,4449449999,4449494999,
%T A087534 4494494999,4494499949,4494949499,4494994499,4499449949,4499494949,
%U A087534 4499944949,4944499949,4949444999,4994449949,9444499949,9444994499,9449494499,9449494949,9499444499,9944944949
%N A087534 Primes consisting only of digits 4 and 9 occurring with equal frequency.
%C A087534 There are 18 digit pairs which can produce such primes. (1,0),(1,3),(1,4),(1,6),(1,7),(1,9),(2,3),(2,9),(3,4),(3,5),(3,7),(3,8),(4,7),(4,9),(5,9),(6,7),(7,9),(8,9).
%H A087534 Harvey P. Dale, <a href="/A087534/b087534.txt">Table of n, a(n) for n = 1..10000</a>
%t A087534 Sort[Flatten[Table[Select[FromDigits/@Permutations[PadRight[{},2n,{4,9}]],PrimeQ],{n,5}]]] (* _Harvey P. Dale_, Aug 21 2016 *)
%o A087534 (PARI)\\ Needs B() from A087510.
%o A087534 concat(vector(6,k,B(k,4,9,isprime)))
%Y A087534 Cf. A087510, A087511, A087533.
%K A087534 base,nonn
%O A087534 1,1
%A A087534 _Paul D. Hanna_ and _Amarnath Murthy_, Sep 12 2003
%E A087534 Edited by _Charles R Greathouse IV_, Oct 28 2009
%E A087534 Offset changed by _Andrew Howroyd_, Sep 20 2024