A344963 Numbers k such that (2*k+1)*k!+1 is prime.

0, 2, 3, 5, 11, 18, 68, 77, 124, 173, 205, 293, 1037, 1530, 1905, 2342, 3401, 4372, 4679, 5385

Offset

1,2

Comments

a(21) > 10^4.

Links

Table of n, a(n) for n=1..20.

Maple

select(k -> isprime((2*k+1)*k!+1), [$0 .. 300])[];

Mathematica

Do[If[PrimeQ[(2*k + 1)*Factorial[k] + 1], Print[k]], {k, 0, 3000}]

Prog

(PARI) for(k=0, 3000, if(isprime((2*k+1)*k!+1), print1(k", ")))
(SageMath)
for k in range(3000):
    if is_prime((2*k+1)*factorial(k) + 1):
        print(k)

Crossrefs

Cf. A002981, A344991.

Sequence in context: A057652 A025067 A024371 * A231479 A084758 A087582

Adjacent sequences: A344960 A344961 A344962 * A344964 A344965 A344966

Keyword

nonn,hard,more

Author

Reza K Ghazi, Jun 07 2021

Status

approved