A105180 Numbers k such that 2^(2*k+1) + 2^k + 1 is prime.

1, 2, 3, 5, 9, 25, 34, 36, 42, 52, 176, 262, 269, 283, 284, 289, 372, 392, 486, 596, 999, 1022, 1097, 1105, 2329, 2663, 3037, 3363, 3853, 5167, 6305, 7164, 7283, 8874, 10974, 14450, 14763, 15016, 15320, 24869, 27192, 35164, 37595, 43540

Offset

1,2

Comments

a(36) > 11800. - Jinyuan Wang, Mar 19 2020

Links

Table of n, a(n) for n=1..44.

Example

2^3 + 2^1 + 1 = 11 prime so a(1) = 1.
2^5 + 2^2 + 1 = 37 prime so a(2) = 2.
2^7 + 2^3 + 1 = 137 prime so a(3) = 3.

Prog

(PARI) is(n)=ispseudoprime(2^(2*n+1)+2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A287915 A354141 A379694 * A094206 A278119 A118998

Adjacent sequences: A105177 A105178 A105179 * A105181 A105182 A105183

Keyword

nonn,more

Author

Pierre CAMI, Apr 11 2005

Extensions

a(34)-a(35) from Jinyuan Wang, Mar 19 2020

a(36)-a(41) from Jeppe Stig Nielsen, Jun 16 2020

a(42)-a(44) from Jorge Coveiro, Apr 10 2023

Status

approved