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A215780
Primes of the form 2*k!! - 1.
2
3, 5, 29, 1889, 20789, 270269, 15811707161249, 443286190953399543749, 433724868863888852244234239999, 163685683629861106170483229851647999999, 10144121732653119949813597183199268946575359999999, 67476497990875549413061344119283906281177486718749
OFFSET
1,1
COMMENTS
The corresponding k are in A215779.
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
Sequence in context: A100857 A100856 A100858 * A214655 A341037 A181429
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 23 2012
EXTENSIONS
Offset changed to 1 by Jinyuan Wang, May 15 2021
STATUS
approved