A215780 Primes of the form 2*k!! - 1.

3, 5, 29, 1889, 20789, 270269, 15811707161249, 443286190953399543749, 433724868863888852244234239999, 163685683629861106170483229851647999999, 10144121732653119949813597183199268946575359999999, 67476497990875549413061344119283906281177486718749

Offset

1,1

Comments

The corresponding k are in A215779.

Links

Table of n, a(n) for n=1..12.

Example

29 =  2*5!! - 1 = 2*15 - 1 is in the sequence.

Mathematica

a={}; Do[p= 2*n!! -1; If[PrimeQ[p], AppendTo[a, p]], {n, 0, 800}]; Print[a];
Select[2 Range[70]!!-1, PrimeQ] (* Harvey P. Dale, Dec 31 2020 *)

Crossrefs

Cf. A006882, A215779.

Sequence in context: A100857 A100856 A100858 * A214655 A341037 A181429

Adjacent sequences: A215777 A215778 A215779 * A215781 A215782 A215783

Keyword

nonn

Author

Michel Lagneau, Aug 23 2012

Extensions

Offset changed to 1 by Jinyuan Wang, May 15 2021

Status

approved