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A288158 a(n) = smallest k such that k*n*2^n-1 is prime. 2
2, 1, 1, 2, 3, 1, 3, 3, 5, 2, 9, 5, 7, 4, 3, 14, 8, 4, 4, 9, 11, 8, 3, 7, 9, 10, 2, 36, 3, 1, 4, 6, 4, 2, 17, 3, 7, 4, 6, 14, 17, 14, 51, 3, 9, 12, 38, 8, 13, 36, 64, 30, 14, 14, 4, 19, 13, 41, 5, 19, 4, 60, 8, 20, 3, 13, 24, 10, 31, 15, 14, 42, 19, 13, 1, 30, 11, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If k = 1 then n*2^n-1 is a Woodall prime (A050918).

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, 78}] (* Michael De Vlieger, Jun 07 2017 *)

PROG

(PARI) a(n) = my(k=1); while(1, if(ispseudoprime(k*n*2^n-1), return(k)); k++) \\ Felix Fröhlich, Jun 06 2017

CROSSREFS

Cf. A050918.

Sequence in context: A153452 A090680 A133771 * A319522 A217612 A029254

Adjacent sequences:  A288155 A288156 A288157 * A288159 A288160 A288161

KEYWORD

nonn

AUTHOR

Pierre CAMI, Jun 06 2017

STATUS

approved

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Last modified February 18 04:48 EST 2020. Contains 332011 sequences. (Running on oeis4.)