A064213 Least k such that k*3^n +- 1 are twin primes.

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

Harry J. Smith, Table of n, a(n) for n = 0..225

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

Adjacent sequences: A064210 A064211 A064212 * A064214 A064215 A064216

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