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 A002254 M2635 N1046 #44 Feb 16 2025 08:32:25
%S A002254 1,3,7,13,15,25,39,55,75,85,127,1947,3313,4687,5947,13165,23473,26607,
%T A002254 125413,209787,240937,819739,1282755,1320487,1777515
%N A002254 Numbers k such that 5*2^k + 1 is prime.
%D A002254 H. Riesel, "Prime numbers and computer methods for factorization," Progress in Mathematics, Vol. 57, Birkhauser, Boston, 1985, Chap. 4, see pp. 381-384.
%D A002254 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002254 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002254 Ray Ballinger, <a href="http://www.prothsearch.com/index.html">Proth Search Page</a>
%H A002254 Ray Ballinger and Wilfrid Keller, <a href="http://www.prothsearch.com/riesel1.html">List of primes k.2^n + 1 for k < 300</a>
%H A002254 C. K. Caldwell, <a href="http://www.utm.edu/research/primes/">The Prime Pages</a>
%H A002254 Y. Gallot, <a href="http://www.utm.edu/research/primes/programs/gallot/index.html">Proth.exe: Windows Program for Finding Large Primes</a>
%H A002254 Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a>
%H A002254 R. M. Robinson, <a href="https://doi.org/10.1090/S0002-9939-1958-0096614-7">A report on primes of the form k.2^n+1 and on factors of Fermat numbers</a>, Proc. Amer. Math. Soc., 9 (1958), 673-681.
%H A002254 R. M. Robinson, <a href="/A002253/a002253_1.pdf"> A report on primes of the form k.2^n+1 and on factors of Fermat numbers</a>, Proc. Amer. Math. Soc., 9 (1958), 673-681. [Annotated scanned copy of selected pages. The first page is (accidentally) included with the scan of the Wilson letter below.]
%H A002254 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ProthPrime.html">Proth Prime</a>
%H A002254 R. G. Wilson v, <a href="/A002253/a002253.pdf">Letter (FAX) to N. J. A. Sloane, May 20 1994, concerning A002253-A002274, A000043, A002235-A002240, A001770-A001775, A007117, and many other sequences</a>
%H A002254 <a href="/index/Pri#riesel">Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime</a>
%t A002254 lst={};Do[If[PrimeQ[5*2^n+1], AppendTo[lst, n]], {n, 0, 2*10^3}];lst (* _Vladimir Joseph Stephan Orlovsky_, Aug 19 2008 *)
%o A002254 (PARI) is(n)=isprime(5*2^n+1) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y A002254 Cf. A050526.
%K A002254 hard,more,nonn
%O A002254 1,2
%A A002254 _N. J. A. Sloane_
%E A002254 Corrected (removed incorrect term 40937) and added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), _Joerg Arndt_, Apr 07 2013