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 A050524 #12 Oct 01 2021 17:43:55 %S A050524 17,71,1151,73727,294911,18874367,79164837199871,83010348331692982271, %T A050524 5704427701027032306735164424191,5841333965851681082096808370372607, %U A050524 6576757367989063131916581747223273588451696443391 %N A050524 Primes of the form 9*2^n-1. %H A050524 <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 A050524 Select[9 2^Range[0,160]-1,PrimeQ] (* _Harvey P. Dale_, Apr 13 2011 *) %Y A050524 See A002236 for more terms. %K A050524 nonn,nice %O A050524 1,1 %A A050524 _N. J. A. Sloane_, Dec 29 1999