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A256823 Numbers n such that A257378(n)=A257379(n), so the prime numbers k*n*2^n-1 and k*n*2^n+1 are twin primes for the smallest k such that k*n*2^n-1 is a prime number. 0
4, 7, 9, 11, 27, 40, 63, 80, 120, 173, 227, 358, 445, 525, 767, 1164, 2180, 5368, 7898 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The k values are in A257378 and A257379.

LINKS

Table of n, a(n) for n=1..19.

PROG

(PARI) a8(n) = my(k=1); while(!isprime(k*n*2^n+1), k+=2); k;

a9(n) = my(k=1); while(!isprime(k*n*2^n-1), k+=2); k;

isok(n) = a8(n) == a9(n); \\ Michel Marcus, Sep 15 2019

CROSSREFS

Cf. A257378, A257379.

Sequence in context: A310949 A139586 A310950 * A074341 A085922 A048973

Adjacent sequences:  A256820 A256821 A256822 * A256824 A256825 A256826

KEYWORD

nonn,more

AUTHOR

Pierre CAMI, Apr 24 2015

STATUS

approved

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Last modified November 18 12:16 EST 2019. Contains 329261 sequences. (Running on oeis4.)