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A076133 Numbers k such that 2*k! - 1 is prime. 11
2, 3, 4, 5, 6, 7, 14, 15, 17, 22, 28, 91, 253, 257, 298, 659, 832, 866, 1849, 2495, 2716, 2773, 2831, 3364, 5264, 7429, 28539, 32123, 37868 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..29.

EXAMPLE

k = 5 is here because 2*5! - 1 = 239 is prime.

MATHEMATICA

Select[Range[8000], PrimeQ[2 #! - 1] &] (* Vincenzo Librandi, Feb 20 2015 *)

PROG

(MAGMA) [n: n in [1..600] | IsPrime(2*Factorial(n)-1)]; // Vincenzo Librandi, Feb 20 2015

(PARI) is(k) = ispseudoprime(2*k!-1); \\ Jinyuan Wang, Feb 04 2020

CROSSREFS

Cf. A051915.

Cf. A002982, A076134, A099350, A099351, A180627, A180628, A180629, A180630, A180631.

Sequence in context: A319723 A271377 A066336 * A277908 A032862 A032886

Adjacent sequences:  A076130 A076131 A076132 * A076134 A076135 A076136

KEYWORD

nonn,more

AUTHOR

Phillip L. Poplin (plpoplin(AT)bellsouth.net), Oct 30 2002

EXTENSIONS

a(24)-a(29) from Serge Batalov, Feb 18 2015

STATUS

approved

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Last modified April 3 16:46 EDT 2020. Contains 333197 sequences. (Running on oeis4.)