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A064213
Least k such that k*3^n +- 1 are twin primes.
5
4, 2, 2, 4, 10, 40, 58, 64, 28, 24, 8, 210, 70, 36, 12, 4, 78, 26, 28, 20, 90, 30, 10, 630, 210, 70, 82, 416, 612, 204, 68, 930, 310, 406, 1078, 1164, 388, 176, 190, 334, 190, 726, 242, 1004, 398, 1430, 1372, 2730, 910, 1560, 520
OFFSET
0,1
COMMENTS
k must be even because 3^n is odd. - Harry J. Smith, Sep 10 2009
LINKS
MATHEMATICA
Do[ k = 1; While[ ! PrimeQ[ k*3^n + 1 ] || ! PrimeQ[ k*3^n - 1 ], k++ ]; Print[ k ], {n, 0, 50} ]
PROG
(PARI) { for (n=0, 225, k=0; p=3^n; until (isprime(k*p - 1) && isprime(k*p + 1), k+=2); write("b064213.txt", n, " ", k); ) } \\ Harry J. Smith, Sep 10 2009
CROSSREFS
Cf. A063983.
Sequence in context: A126560 A289762 A360855 * A354102 A245518 A217462
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Sep 21 2001
EXTENSIONS
Offset changed from 1 to 0 by Harry J. Smith, Sep 10 2009
STATUS
approved