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A290116
Primes of the form k! / 2 - 1.
1
2, 11, 59, 359, 181439, 4111419327088961408862781439999999, 16726263306581903554085031026720375832575999999999
OFFSET
1,1
FORMULA
a = (A082671(n)!-2)/2.
EXAMPLE
6! / 2 - 1 = 359, which is prime, so 359 is in the sequence.
7! / 2 - 1 = 2519 = 11 * 229, so 2519 is not in the sequence.
MATHEMATICA
Select[Table[k! / 2 - 1, {k, 2, 100}], PrimeQ[#]&]
CROSSREFS
Sequence in context: A280674 A139172 A228868 * A251180 A286194 A164034
KEYWORD
nonn
AUTHOR
Robert Price, Jul 19 2017
STATUS
approved