OFFSET
1,1
COMMENTS
p and p^2 + 2^p are both prime only for p=3. All positive n satisfy the congruence n=3 (mod 6). - Lekraj Beedassy, Sep 07 2004
For values of n, see A064539. - Lekraj Beedassy, Jan 01 2007
The next term has 605 digits. - Harvey P. Dale, Jul 19 2017
REFERENCES
J.-M. De Koninck & A. Mercier, 1001 Problemes en Theorie Classique Des Nombres,Problem 165 pp. 30; 160, Ellipses Paris 2004.
EXAMPLE
a(3) = 593 = 2^9 +9^2. a(4) = 32993= 2^15 + 15^2.
MATHEMATICA
Select[Table[n^2+2^n, {n, 1000}], PrimeQ] (* Harvey P. Dale, Jul 19 2017 *)
PROG
(PARI) for(n=1, 10^7, if(isprime(n^2+2^n), print(n^2+2^n)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Apr 21 2001
EXTENSIONS
More terms from Jason Earls, Aug 09 2001. Next term too large to include.
STATUS
approved