A242487 Numbers k such that (2*k)! + k! + 1 is prime.

0, 3, 8, 13, 19, 423, 585, 2746, 2855

Offset

1,2

Links

Table of n, a(n) for n=1..9.

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.

Cf. A002981, A237443.

Sequence in context: A081989 A264780 A208276 * A335869 A303592 A120883

Adjacent sequences: A242484 A242485 A242486 * A242488 A242489 A242490

Keyword

nonn,more

Author

Seiichi Manyama, Mar 22 2018

Extensions

a(8)-a(9) from Michael S. Branicky, Apr 16 2023

Status

approved