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 A127995 #30 May 05 2023 15:24:03 %S A127995 3,11,17,1487,31013,48859,61403,472709,984349 %N A127995 Numbers k such that (20^k - 1)/19 is prime. %H A127995 Paul Bourdelais, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=NMBRTHRY;417ab0d6.0906">A Generalized Repunit Conjecture</a> %H A127995 H. Dubner, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1185243-9">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930. %H A127995 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a> %H A127995 <a href="/index/Pri#primepop">Index to primes in various ranges</a>, form ((k+1)^n-1)/k %t A127995 Select[Prime[Range[100]],PrimeQ[(20^#-1)/19]&] %o A127995 (PARI) is(n)=isprime((20^n-1)/19) \\ _Charles R Greathouse IV_, Feb 17 2017 %K A127995 hard,more,nonn %O A127995 1,1 %A A127995 _Alexander Adamchuk_, Feb 11 2007 %E A127995 One more term from _Ryan Propper_, Mar 29 2007 %E A127995 a(5) & a(6) are probable primes found by _Paul Bourdelais_, Mar 05 2010 %E A127995 a(7) is a probable prime found by _Paul Bourdelais_, Mar 08 2010 %E A127995 a(8) is a probable prime found by _Paul Bourdelais_, Jan 15 2015 %E A127995 a(9) from _Paul Bourdelais_, Sep 13 2021