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

8, 9, 10, 11, 19, 55, 125, 953

Offset

1,1

Links

Table of n, a(n) for n=1..8.

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

Sequence in context: A297134 A247455 A280290 * A323062 A097363 A152870

Adjacent sequences: A138578 A138579 A138580 * A138582 A138583 A138584

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, May 13 2008

Extensions

One more term (a(8)) from Harvey P. Dale, Jul 11 2023

Status

approved