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A061119 Primes in the sequence n^2 + 2^n (A001580). 9
3, 17, 593, 32993, 2097593, 8589935681 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=1..6.

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

Subsequence of A094133.

Cf. A001580, A075896.

Sequence in context: A128300 A292082 A001601 * A094133 A049985 A126579

Adjacent sequences:  A061116 A061117 A061118 * A061120 A061121 A061122

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

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Last modified October 17 08:36 EDT 2019. Contains 328107 sequences. (Running on oeis4.)