A215777 Primes of the form 2*k!! + 1.

3, 3, 5, 7, 17, 31, 97, 211, 769, 7681, 270271, 68918851, 371589121, 3923981107201, 2856658246041601, 85699747381248001, 639661973545755541631251, 5960455827486621749452458387843751

Offset

1,1

Comments

The corresponding k are in A215775.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..23

Example

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

Mathematica

lst={}; Do[If[PrimeQ[p = 2 n!! + 1], AppendTo[lst, p]], {n, 0, 60}]; lst
Select[Table[2 n!! + 1, {n, 0, 60}], PrimeQ] (* Vincenzo Librandi, Oct 01 2012 *)

Crossrefs

Cf. A006882, A215775, A215780.

Sequence in context: A352912 A240180 A169942 * A147095 A161626 A217648

Adjacent sequences: A215774 A215775 A215776 * A215778 A215779 A215780

Keyword

nonn

Author

Michel Lagneau, Aug 23 2012

Extensions

Offset corrected from 0 to 1 by Vincenzo Librandi, Oct 01 2012

Status

approved