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 A087537 #12 Sep 20 2024 23:54:27 %S A087537 79,97,77997979,79779979,79797997,79997977,99977797,99979777, %T A087537 7777997999,7779799799,7779799997,7779979979,7797799979,7797979799, %U A087537 7799797799,7977799799,7979799977,7979979779,7979979797,7979979977,7979997797,7997799977,7997979779,7997997977 %N A087537 Primes consisting only of digits 7 and 9 occurring with equal frequency. %C A087537 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 A087537 Andrew Howroyd, <a href="/A087537/b087537.txt">Table of n, a(n) for n = 1..9931</a> %o A087537 (PARI) \\ Needs B() from A087510. %o A087537 concat(vector(6,k,B(k,7,9,isprime))) \\ _Andrew Howroyd_, Sep 20 2024 %Y A087537 Cf. A087510, A087511, A087536. %K A087537 base,nonn %O A087537 1,1 %A A087537 _Amarnath Murthy_ and _Paul D. Hanna_, Sep 12 2003 %E A087537 Edited by _Charles R Greathouse IV_, Oct 28 2009 %E A087537 Offset changed and a(22) onwards from _Andrew Howroyd_, Sep 20 2024