Primes of the form 2^(k-1)+k

[zei...@indmath.uni-linz.ac.at]

Kevin BROWN of Delphi Internet Services Organisation asks:

> The solution of a problem I am working on requires primes of the form
>
> 2^(k-1) + k = prime
>
> So far the only values I can find with k < 1000 are k = 1, 3, 7, and 237.
> Can anyone confirm this? Also, can anyone find any more values of k that
> produce primes?

Maple does confirm and is still working for more values.
It found already k=1885.

Helmut Zeisel

[Robert D. Silverman]

In article <0097A8D9.ED...@indmath.uni-linz.ac.at> zei...@indmath.uni-linz.ac.at writes:
:Kevin BROWN of Delphi Internet Services Organisation asks:

Heuristically, I would expect #{k < N such that 2^(k-1)+k is prime}
to be about log log N.
--
Bob Silverman
These are my opinions and not MITRE's.
Mitre Corporation, Bedford, MA 01730
"You can lead a horse's ass to knowledge, but you can't make him think"