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 A173803 #7 Jun 01 2019 13:30:52 %S A173803 11,31,71,151,311,631,2551,655351,2621431,10485751,5497558138871, %T A173803 10995116277751,175921860444151,737869762948382064631, %U A173803 396140812571321687967719751671 %N A173803 Primes in A139634. %t A173803 Select[10*2^Range[0,100]-9,PrimeQ] (* _Harvey P. Dale_, Jun 01 2019 *) %Y A173803 Cf. A139634 %K A173803 nonn %O A173803 1,1 %A A173803 _Vincenzo Librandi_, Mar 05 2010 %E A173803 Edited by _Jon E. Schoenfield_, Jun 23 2010