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 A087514 #18 Sep 21 2024 12:25:17
%S A087514 17,71,11171777,11177717,17111777,17171177,17171771,17177117,17711717,
%T A087514 17717171,71117177,71171717,71717117,77111717,77711171,1111717777,
%U A087514 1117117777,1117177177,1117771177,1117771717,1177117177,1177177711,1177711177,1177717171,1177717711
%N A087514 Primes consisting only of digits 1 and 7 occurring with equal frequency.
%C A087514 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 A087514 Andrew Howroyd, <a href="/A087514/b087514.txt">Table of n, a(n) for n = 1..10444</a> (first 1001 terms from Harvey P. Dale)
%t A087514 Sort[Select[FromDigits/@Flatten[Table[Permutations[PadRight[{},2n,{1,7}]],{n,5}],1],PrimeQ]] (* _Harvey P. Dale_, Jul 27 2019 *)
%o A087514 (PARI) \\ Needs B() from A087510.
%o A087514 concat(vector(6,k,B(k,1,7,isprime))) \\ _Andrew Howroyd_, Sep 21 2024
%Y A087514 Cf. A087510, A087511, A087513.
%K A087514 base,nonn
%O A087514 1,1
%A A087514 _Amarnath Murthy_ and _Paul D. Hanna_, Sep 11 2003
%E A087514 Offset changed by _Andrew Howroyd_, Sep 21 2024