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.

4, 7, 9, 11, 27, 40, 63, 80, 120, 173, 227, 358, 445, 525, 767, 1164, 2180, 5368, 7898

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 A362185 A085922

Adjacent sequences: A256820 A256821 A256822 * A256824 A256825 A256826

Keyword

nonn,more

Author

Pierre CAMI, Apr 24 2015

Status

approved