;Definition
A ''Wagstaff prime'' is a prime number of the form ''(2^p + 1)/3'' where the exponent ''p'' is an odd prime.

;Example 
(2^5 + 1)/3 = 11 is a Wagstaff prime because both 5 and 11 are primes.

;Task
Find and show here the first ''10'' Wagstaff primes and their corresponding exponents ''p''.

;Stretch (requires arbitrary precision integers)
Find and show here the exponents ''p'' corresponding to the next ''14'' Wagstaff primes (not the primes themselves) and any more that you have the patience for. 

When testing for primality, you may use a method which determines that a large number is probably prime with reasonable certainty.

;Note
It can be shown (see talk page) that ''(2^p + 1)/3'' is always integral if ''p'' is odd. So there's no need to check for that prior to checking for primality.

;References

* [[wp:Wagstaff prime|Wikipedia - Wagstaff prime]]
* [[oeis:A000979|OEIS:A000979 - Wagstaff primes]]
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