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 A059613 #23 Jul 25 2021 18:32:07 %S A059613 5,7,15,47,81,115,267,285,7641,19089,25831,32115,59811,70155,178715 %N A059613 Numbers k such that 5^k - 4 is prime. %C A059613 a(15) > 10^5. - _Robert Price_, Feb 03 2014 %C A059613 a(16) > 2*10^5. - _Tyler NeSmith_, Jul 25 2021 %e A059613 81 is present because 5^81 - 4 is prime. %t A059613 Select[Range[10000], PrimeQ[5^# - 4] &] (* _Vincenzo Librandi_, Oct 03 2012 *) %o A059613 (PARI) is(n)=ispseudoprime(5^n-4) \\ _Charles R Greathouse IV_, Feb 20 2017 %Y A059613 Cf. A164785. %K A059613 nonn,hard,more %O A059613 1,1 %A A059613 _Andrey V. Kulsha_, Feb 07 2001 %E A059613 a(10)-a(14) from _Robert Price_, Feb 03 2014 %E A059613 a(15) from _Tyler NeSmith_, Jul 25 2021