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 A206430 #11 Apr 20 2012 21:17:04
%S A206430 509203,777149,7106977,60014203
%N A206430 Least k such that k*2^m - 1 has a covering set with precisely n primes.
%C A206430 A set of primes is a covering set for k*2^m - 1 if for every positive integer m there is some prime in the set which divides k*2^m - 1. Only minimal covering sets are considered here (those which would not remain covering sets with the removal of any element).
%H A206430 Wikipedia, <a href="http://en.wikipedia.org/wiki/Covering_set">Covering set</a>
%H A206430 Wikipedia, <a href="http://en.wikipedia.org/wiki/Riesel_number">Riesel number</a>
%e A206430 509203 has the covering set {3, 5, 7, 13, 17, 241}.
%e A206430 777149 has the covering set {3, 5, 7, 13, 19, 37, 73}.
%e A206430 7106977 has the covering set {3, 5, 13, 17, 19, 109, 241, 433}.
%e A206430 60014203 has the covering set {3, 5, 7, 11, 13, 31, 41, 61, 151}.
%Y A206430 Cf. A076337, A101036.
%K A206430 more,nonn
%O A206430 6,1
%A A206430 _Arkadiusz Wesolowski_, Apr 19 2012