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 A127999 #21 Feb 17 2017 15:42:37 %S A127999 7,43,347,12421,12473,26717 %N A127999 Numbers n such that (26^n - 1)/25 is prime. %C A127999 The next term after 347 is bigger than 2250. - _Stefan Steinerberger_, May 05 2007 %C A127999 No other terms less than 100000. - _Robert Price_, Mar 18 2012 %H A127999 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 A127999 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a> %H A127999 <a href="/index/Pri#primepop">Index to primes in various ranges</a>, form ((k+1)^n-1)/k %t A127999 Select[Prime[Range[100]], PrimeQ[(26^#-1)/25]&] %o A127999 (PARI) is(n)=ispseudoprime((26^n-1)/25) \\ _Charles R Greathouse IV_, Feb 17 2017 %K A127999 hard,more,nonn %O A127999 1,1 %A A127999 _Alexander Adamchuk_, Feb 11 2007 %E A127999 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008