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 A205771 #10 Mar 30 2012 18:52:15 %S A205771 3,11,251,2441406251,56843418860808014869689941406251, %T A205771 49303806576313237838233035330174139354575402194313937798142433166503906251 %N A205771 Primes of the form 2*5^n+1. %H A205771 Vincenzo Librandi, <a href="/A205771/b205771.txt">Table of n, a(n) for n = 1..9</a> %t A205771 Select[2*5^Range[0, 500] + 1, PrimeQ] %Y A205771 Cf. A058934 %K A205771 nonn %O A205771 1,1 %A A205771 _Vladimir Joseph Stephan Orlovsky_, Jan 31 2012