A288159 a(n) = smallest k such that k*n*2^n+1 is prime.

1, 2, 3, 3, 4, 2, 3, 6, 4, 4, 9, 3, 3, 5, 9, 7, 3, 3, 3, 5, 3, 7, 19, 5, 5, 2, 3, 7, 7, 9, 5, 15, 3, 10, 10, 7, 14, 6, 8, 6, 25, 6, 50, 45, 13, 4, 18, 31, 27, 2, 4, 33, 18, 2, 41, 18, 10, 9, 6, 7, 3, 32, 4, 39, 18, 17, 11, 30, 17, 18, 7, 51, 38, 11, 15, 13, 9, 10, 24, 2

Offset

1,2

Comments

If k = 1 then n*2^n+1 is a Cullen prime (A050920).

Links

Pierre CAMI, Table of n, a(n) for n = 1..10000

Mathematica

Table[k = 1; While[! PrimeQ[k n*2^n + 1], k++]; k, {n, 80}] (* Michael De Vlieger, Jun 09 2017 *)

Prog

(PARI) a(n) = my(k=1); while (! isprime(k*n*2^n+1), k++); k; \\ Michel Marcus, Jun 07 2017

Crossrefs

Cf. A050920, A288158.

Sequence in context: A361819 A304758 A103893 * A269526 A106448 A295280

Adjacent sequences: A288156 A288157 A288158 * A288160 A288161 A288162

Keyword

nonn

Author

Pierre CAMI, Jun 06 2017

Status

approved