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A105181 Numbers k such that 2^(2*(k+1)) + 2^k - 1 is prime. 1
1, 2, 3, 4, 5, 6, 8, 10, 14, 22, 38, 42, 71, 118, 128, 159, 179, 214, 484, 951, 1148, 1162, 1427, 1532, 1692, 1861, 2261, 3760, 4575, 6974, 7295, 8367, 8463, 8600, 14878, 16165 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

EXAMPLE

2^4 + 2^1 + 1 = 19 is prime so a(1)=1.

2^6 + 2^2 + 1 = 67 is prime so a(2)=2.

2^8 + 2^3 + 1 = 263 is prime so a(3)=3.

MATHEMATICA

a[n_]:=2^(2*(n+1))+2^n-1; lst={}; Do[If[PrimeQ[a[n]], AppendTo[lst, n]], {n, 0, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Jan 03 2009 *)

PROG

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

(Magma) [k: k in [0..200] | IsPrime(2^(2*(k+1))+2^k-1)]; // Jinyuan Wang, Mar 20 2020

CROSSREFS

Cf. A105182.

Sequence in context: A179053 A218949 A129976 * A263361 A320020 A229034

Adjacent sequences: A105178 A105179 A105180 * A105182 A105183 A105184

KEYWORD

nonn,more

AUTHOR

Pierre CAMI, Apr 11 2005

EXTENSIONS

More terms from Ryan Propper, Jan 31 2008

STATUS

approved

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Last modified February 7 07:00 EST 2023. Contains 360112 sequences. (Running on oeis4.)