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A064215 Least k such that k*6^n +/- 1 are twin primes. 2
1, 2, 2, 2, 18, 3, 33, 255, 212, 115, 147, 102, 17, 33, 308, 87, 198, 33, 172, 418, 210, 35, 158, 847, 1010, 292, 157, 1318, 263, 212, 642, 107, 458, 102, 17, 635, 735, 262, 2422, 3517, 1222, 605, 1362, 227, 367, 602, 207, 2023, 3925, 1857, 822, 137, 5568, 928 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

As n increases, a(n) is in average = 0.44*n^2. It appears that 62% of a(n)/n^2 are < 0.44. - Pierre CAMI, Jun 01 2012

LINKS

R. J. Mathar, Table of n, a(n) for n = 1..240

MAPLE

A064215 := proc(n)

    for k from 1 do

        if isprime(k*6^n-1) and isprime(k*6^n+1) then

            return k;

        end if;

    end do:

end proc: # R. J. Mathar, Sep 17 2015

MATHEMATICA

Table[ k = 1; While[ ! PrimeQ[ k*6^n + 1 ] || ! PrimeQ[ k*6^n - 1 ], k++ ]; k, {n, 50} ]

CROSSREFS

Cf. A063983.

Sequence in context: A195871 A214756 A079007 * A087238 A226935 A099640

Adjacent sequences:  A064212 A064213 A064214 * A064216 A064217 A064218

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Sep 21 2001

STATUS

approved

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Last modified November 17 16:08 EST 2019. Contains 329241 sequences. (Running on oeis4.)