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A062326 Primes p such that p^2 - 2 is also prime. 39
2, 3, 5, 7, 13, 19, 29, 37, 43, 47, 61, 71, 89, 103, 107, 127, 131, 139, 173, 191, 211, 223, 233, 239, 257, 293, 313, 337, 359, 421, 443, 449, 467, 491, 523, 541, 569, 587, 607, 653, 677, 719, 727, 733, 743, 751, 757, 761, 797, 811, 863, 881, 1013, 1021 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

When p and p^2 - 2 are both prime, the fundamental solution of the Pell equation x^2 - n*y^2 = 1, for n = p^2 - 2, is x = p^2 - 1 and y = p. See A109748 for the case of n and x both prime. - T. D. Noe, May 19 2007

Solutions of the equation n' + (n^2-2)' = 2, where n' is the arithmetic derivative of n. - Paolo P. Lava, Nov 09 2012

3 is the only prime p such that p^2 + 2 and p^2 - 2 are both primes. - Jaroslav Krizek, Nov 25 2013 (note that p^2 + 2 is composite for all primes p >= 5. - Joerg Arndt, Jan 10 2015)

For all primes p except for p = 3, p^2 + 2 is multiple of 3 (see A061725). - Zak Seidov, Feb 19 2015

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Prime[Range[500]], PrimeQ[#^2 - 2] &] (* Harvey P. Dale, Sep 20 2011 *)

PROG

(MAGMA) [ p: p in PrimesUpTo(1100) | IsPrime(p^2-2) ]; // Klaus Brockhaus, Jan 01 2009

(PARI) { n=0; forprime (p=2, 5*10^5, if (isprime(p^2 - 2), write("b062326.txt", n++, " ", p); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 05 2009

(Haskell)

import Data.List (elemIndices)

a062326 = a000040 . a137291

a062326_list = map (a000040 . (+ 1)) $

               elemIndices 1 $ map a010051' a049001_list

-- Reinhard Zumkeller, Jul 30 2015

CROSSREFS

Cf. A049002 (p^2-2).

Cf. A137291, A010051, A004901, A000040.

Sequence in context: A147791 A169647 A072467 * A198273 A066076 A136288

Adjacent sequences:  A062323 A062324 A062325 * A062327 A062328 A062329

KEYWORD

nonn,nice

AUTHOR

Reiner Martin (reinermartin(AT)hotmail.com), Jul 12 2001

STATUS

approved

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Last modified January 19 21:35 EST 2018. Contains 297938 sequences.