A344170 Numbers k such that 3^(2*k+1) - 3^k - 1 is prime.

1, 2, 5, 6, 7, 10, 17, 25, 31, 88, 95, 137, 141, 416, 610, 781, 800, 2353, 7291, 9627, 9749, 15946, 19215

Offset

1,2

Comments

a(24) > 20000.

Links

Table of n, a(n) for n=1..23.

Maple

for k from 1 to 3000 do if isprime(3^(2*k + 1) - 3^k - 1) then print(k); end if; end do

Mathematica

Do[If[PrimeQ[3^(2k + 1) - 3^k - 1], Print[k]], {k, 1, 3000}]

Prog

(PARI) for(k=1, 3e3, if(isprime(3^(2*k+1)-3^k-1), print1(k", ")))
(SageMath)
for k in range(1, 3000):
    if is_prime(3^(2 * k + 1) - 3^k - 1):
        print(k)

Crossrefs

Cf. A344263.

Sequence in context: A284393 A287366 A080589 * A292115 A283476 A059791

Adjacent sequences: A344167 A344168 A344169 * A344171 A344172 A344173

Keyword

nonn,more

Author

Reza K Ghazi, May 10 2021

Extensions

a(19)-a(21) from Michael S. Branicky, May 11 2021

a(22)-a(23) from Reza K Ghazi, May 14 2021

Status

approved