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 A215777 #28 May 15 2021 11:48:30
%S A215777 3,3,5,7,17,31,97,211,769,7681,270271,68918851,371589121,
%T A215777 3923981107201,2856658246041601,85699747381248001,
%U A215777 639661973545755541631251,5960455827486621749452458387843751
%N A215777 Primes of the form 2*k!! + 1.
%C A215777 The corresponding k are in A215775.
%H A215777 Vincenzo Librandi, <a href="/A215777/b215777.txt">Table of n, a(n) for n = 1..23</a>
%e A215777 68918851 = 2*17!! + 1 = 2*34459425 + 1 is in the sequence.
%t A215777 lst={}; Do[If[PrimeQ[p = 2 n!! + 1], AppendTo[lst, p]], {n, 0, 60}]; lst
%t A215777 Select[Table[2 n!! + 1, {n, 0, 60}], PrimeQ] (* _Vincenzo Librandi_, Oct 01 2012 *)
%Y A215777 Cf. A006882, A215775, A215780.
%K A215777 nonn
%O A215777 1,1
%A A215777 _Michel Lagneau_, Aug 23 2012
%E A215777 Offset corrected from 0 to 1 by _Vincenzo Librandi_, Oct 01 2012