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

Author

Michel Lagneau, Aug 23 2012

Keywords

• nonn

Comments

The corresponding k are in A215775.

Examples

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

Links

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

Crossrefs

Cf. A006882, A215775, A215780.

Programs

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 *)

Extensions

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