A138577 Numbers k such that 2^(2*k-3) - 3 is prime.

3, 4, 6, 16, 108, 112, 118, 274, 346, 1162, 1620, 10380, 15022, 21346, 22316, 34670, 61650

Offset

1,1

Links

Table of n, a(n) for n=1..17.

Example

2^(2*3-3)-3 = 5, 2^(2*4-3)-3 = 29, 2^(2*6-3)-3 = 509, ... .

Mathematica

q=3; For[i=q, i<=q, a={}; Do[x=2^(2*n-i)-i; If[PrimeQ[x], AppendTo[a, n]], {n, 10^2}]; Print["2^(2*n-", i, ")-", i, " ", a]; i=i+2]
Select[Range[400], PrimeQ[2^(2#-3)-3]&] (* Harvey P. Dale, Aug 10 2017 *)

Prog

(PARI) is(n)=isprime(2^(2*n-3)-3) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A138578, A138579, A138580, A138581, A138582.

Cf. A138598, A138599, A138600, A138601, A138602, A138603.

Sequence in context: A092933 A122849 A068573 * A394081 A298149 A136242

Adjacent sequences: A138574 A138575 A138576 * A138578 A138579 A138580

Keyword

nonn,more

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

a(10)-a(11) from Harvey P. Dale, Aug 10 2017

a(12)-a(17) from Michael S. Branicky, May 20 2026

Status

approved