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A130327 Least prime p such that 3*p*2^n-1 and 3*p*2^n+1 are twin primes. 4
2, 2, 5, 3, 5, 2, 11, 3, 19, 17, 5, 113, 59, 317, 331, 307, 241, 2, 829, 23, 149, 127, 11, 3023, 1091, 787, 971, 1523, 2741, 727, 1051, 227, 211, 727, 89, 1163, 71, 367, 1031, 577, 89, 1213, 1151, 3, 1021, 283, 2699, 4933, 59, 647, 709 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Pierre CAMI, Table of n, a(n) for n = 0..200

EXAMPLE

3*2*2^0-1=5, 3*2*2^0+1=7: 5 and 7 are twin primes so for n=0 p=2.

3*2*2^1-1=11, 3*2*2^1+1=13: 11 and 13 are twin primes so for n=1 p=2.

PROG

(PARI) a(n) = my(p=2); while (!(isprime(q=3*p*2^n-1) && isprime(q+2)), p=nextprime(p+1)); p; \\ Michel Marcus, Sep 23 2019

CROSSREFS

Cf. A130325, A130326.

Sequence in context: A128134 A157223 A174608 * A224361 A286109 A239665

Adjacent sequences:  A130324 A130325 A130326 * A130328 A130329 A130330

KEYWORD

nonn

AUTHOR

Pierre CAMI, May 24 2007

STATUS

approved

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Last modified May 29 20:42 EDT 2020. Contains 334710 sequences. (Running on oeis4.)