A344991 Numbers k such that (2*k+1)*k!-1 is prime.

1, 3, 5, 15, 20, 44, 45, 73, 80, 93, 295, 5395

Offset

1,2

Comments

a(13) > 10^4.

Links

Table of n, a(n) for n=1..12.

Maple

select(k -> isprime((2*k+1)*k!-1), [$1 .. 300])[];

Mathematica

Do[If[PrimeQ[(2*k + 1)*Factorial[k] - 1], Print[k]], {k, 1, 3000}]

Prog

(PARI) for(k=1, 3000, if(isprime((2*k+1)*k!-1), print1(k", ")))
(SageMath)
for k in range(1, 3000):
    if is_prime((2*k+1)*factorial(k) - 1):
        print(k)

Crossrefs

Cf. A002982, A344963.

Sequence in context: A220164 A018374 A290297 * A063185 A208854 A165260

Adjacent sequences: A344988 A344989 A344990 * A344992 A344993 A344994

Keyword

nonn,hard,more

Author

Reza K Ghazi, Jun 07 2021

Status

approved