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A303737 Numbers k such that (2*k)! + k! - 1 is prime. 1
1, 4, 18, 49, 60, 82, 321, 6328 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(9) > 10000. - Giovanni Resta, Jun 07 2018

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

1 is a term because (2*1)! + 1! - 1 = 2 which is a prime.

4 is a term because (2*4)! + 4! - 1 = 40343 which is a prime.

MAPLE

select(k->isprime(factorial(2*k)+factorial(k)-1), [$1..1000]);

PROG

(PARI) isok(k) = isprime((2*k)! + k! - 1); \\ Michel Marcus, May 28 2018

CROSSREFS

Cf. A242487, A300947, A303738 (corresponding primes).

Sequence in context: A081528 A056147 A181857 * A180805 A120656 A256431

Adjacent sequences:  A303734 A303735 A303736 * A303738 A303739 A303740

KEYWORD

nonn,more

AUTHOR

Muniru A Asiru, May 27 2018

EXTENSIONS

a(8) from Giovanni Resta, Jun 07 2018

STATUS

approved

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Last modified March 29 17:23 EDT 2020. Contains 333116 sequences. (Running on oeis4.)