login
A242487
Numbers k such that (2*k)! + k! + 1 is prime.
3
0, 3, 8, 13, 19, 423, 585, 2746, 2855
OFFSET
1,2
EXAMPLE
0! + 0! + 1 = 3 is prime.
6! + 3! + 1 = 727 is prime.
MAPLE
select(k->isprime(factorial(2*k)+factorial(k)+1), [$0..600]); # Muniru A Asiru, May 27 2018
MATHEMATICA
Flatten[{0, Select[Range[100], PrimeQ[(2*#)! + #! + 1] &]}] (* Vaclav Kotesovec, Mar 25 2018 *)
PROG
(PARI) isok(k) = ispseudoprime((2*k)!+k!+1); \\ Altug Alkan, Mar 22 2018
CROSSREFS
A300947 gives the primes.
Sequence in context: A081989 A264780 A208276 * A335869 A303592 A120883
KEYWORD
nonn,more
AUTHOR
Seiichi Manyama, Mar 22 2018
EXTENSIONS
a(8)-a(9) from Michael S. Branicky, Apr 16 2023
STATUS
approved