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 A050553 #19 Jan 17 2019 10:08:17 %S A050553 1,3,5,7,15,33,41,57,69,75,77,131,133,153,247,305,351,409,471,1251, %T A050553 1259,2253,2411,2425,2699,3221,4099,4173,4291,4905,5349,6723,7143, %U A050553 7505,10539,10557,12099,17373,23721,27895,33801,35519,45927,63589,73287,96933,106659,218043,253047,397941,651015 %N A050553 Numbers n such that 55*2^n-1 is prime. %H A050553 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 A050553 Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a> %H A050553 <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> %H A050553 Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list k<300</a>. %o A050553 (PARI) is(n)=ispseudoprime(55*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A050553 Cf. A057813. %K A050553 hard,nonn %O A050553 1,2 %A A050553 _N. J. A. Sloane_, Dec 29 1999 %E A050553 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008