A138581 Numbers k such that 2^(2*k-15) - 15 is prime.

10, 11, 19, 55, 125, 953, 1924, 3016, 4985, 5707, 14369, 16036, 68687, 69821

Offset

1,1

Links

Table of n, a(n) for n=1..14.

Example

2^(2*11-15)-15 = 113, 2^(2*19-15)-15 = 8388593, 2^(2*55-15)-15 = 39614081257132168796771975153, ... .

Mathematica

q=15; 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[1000], PrimeQ[2^(2#-15)-15]&] (* Harvey P. Dale, Jul 11 2023 *)

Prog

(PARI) is(n)=isprime(2^(2*n-15)-15) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A138577, A138578, A138579, A138580, A138582.

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

Sequence in context: A214790 A191221 A216996 * A165265 A329818 A329447

Adjacent sequences: A138578 A138579 A138580 * A138582 A138583 A138584

Keyword

nonn,more

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

a(6) = 953 from Harvey P. Dale, Jul 11 2023

Terms 8 and 9 removed and a(7)-a(14) from Michael S. Branicky, May 20 2026

Status

approved