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 A290116 #15 Jul 22 2017 10:08:03
%S A290116 2,11,59,359,181439,4111419327088961408862781439999999,
%T A290116 16726263306581903554085031026720375832575999999999
%N A290116 Primes of the form k! / 2 - 1.
%H A290116 Robert Price, <a href="/A290116/b290116.txt">Table of n, a(n) for n = 1..7</a>
%H A290116 Joe McLean, <a href="http://web.archive.org/web/20091027034731/http://uk.geocities.com/nassarawa%40btinternet.com/probprim2.htm">Interesting Sources of Probable Primes</a>
%H A290116 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%F A290116 a = (A082671(n)!-2)/2.
%e A290116 6! / 2 - 1 = 359, which is prime, so 359 is in the sequence.
%e A290116 7! / 2 - 1 = 2519 = 11 * 229, so 2519 is not in the sequence.
%t A290116 Select[Table[k! / 2 - 1, {k, 2, 100}], PrimeQ[#]&]
%Y A290116 Cf. A082671, A139172.
%K A290116 nonn
%O A290116 1,1
%A A290116 _Robert Price_, Jul 19 2017