A215777 - OEIS

%I #28 May 15 2021 11:48:30

%S 3,3,5,7,17,31,97,211,769,7681,270271,68918851,371589121,

%T 3923981107201,2856658246041601,85699747381248001,

%U 639661973545755541631251,5960455827486621749452458387843751

%N Primes of the form 2*k!! + 1.

%C The corresponding k are in A215775.

%H Vincenzo Librandi, <a href="/A215777/b215777.txt">Table of n, a(n) for n = 1..23</a>

%e 68918851 =  2*17!! + 1 = 2*34459425 + 1 is in the sequence.

%t lst={}; Do[If[PrimeQ[p = 2 n!! + 1], AppendTo[lst, p]], {n, 0, 60}]; lst

%t Select[Table[2 n!! + 1, {n, 0, 60}], PrimeQ] (* _Vincenzo Librandi_, Oct 01 2012 *)

%Y Cf. A006882, A215775, A215780.

%K nonn

%O 1,1

%A _Michel Lagneau_, Aug 23 2012

%E Offset corrected from 0 to 1 by _Vincenzo Librandi_, Oct 01 2012