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A239326 Numbers k such that k^2 +/- (k-1) and (k-1)*k^2 +/- 1 are all primes. 2
2, 3, 6, 13, 21, 100, 120, 195, 393, 541, 1749, 1849, 3640, 3829, 4003, 5488, 5754, 8973, 8989, 9043, 10824, 10828, 13488, 17016, 18493, 19306, 21505, 24270, 27139, 30163, 31530, 34134, 35034, 39514, 40761, 46215, 46285, 46398, 49071, 49869, 53319, 55320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A239115 and A239135.

LINKS

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

EXAMPLE

6 is this sequence because (6-1)*6^2-1 = 179, (6-1)*6^2+1 = 181, 6^2-6+1 = 31 and 6^2+6-1 = 41 are all primes.

PROG

(MAGMA) k := 1;

     for n in [1..100000] do

        if IsPrime(k*(n - 1)*n^2 + 1) and IsPrime(k*(n - 1)*n^2 - 1) and IsPrime(k*n^2 + n - 1) and IsPrime(k*n^2 - n + 1) then

           n;

        end if;

     end for;

CROSSREFS

Sequence in context: A175281 A244790 A111503 * A075530 A032061 A155996

Adjacent sequences:  A239323 A239324 A239325 * A239327 A239328 A239329

KEYWORD

nonn,easy

AUTHOR

Ilya Lopatin and Juri-Stepan Gerasimov, Mar 16 2014

EXTENSIONS

Edited by Alois P. Heinz, Mar 19 2014

STATUS

approved

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Last modified August 4 08:25 EDT 2020. Contains 336201 sequences. (Running on oeis4.)