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A157200 Numbers n such that n*(2n)^n-1 is a prime. 0
2, 3, 6, 7, 12, 21, 113, 404, 735, 1944, 4973 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: there are infinite numbers of such kind of primes.

a(12) > 10000. [From Donovan Johnson, Aug 31 2010]

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

n=2, 2*(2*2)^2-1 = 31 is a prime number; n=3, 3^(2*3)^2-1 = 107 is a prime number; and so on

MATHEMATICA

Do[cp=n*(2*n)^n-1; If[PrimeQ[cp], Print[n]], {n, 1, 2000}] This generates the listed first 10 elements.

PROG

(PARI) is(n)=ispseudoprime(n*(2*n)^n-1) \\ Charles R Greathouse IV, Jun 17 2013

CROSSREFS

Sequence in context: A238590 A144120 A073712 * A255940 A167415 A018511

Adjacent sequences:  A157197 A157198 A157199 * A157201 A157202 A157203

KEYWORD

hard,nice,nonn

AUTHOR

Lei Zhou, Feb 25 2009

EXTENSIONS

a(11) from Donovan Johnson, Aug 31 2010

STATUS

approved

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Last modified December 16 03:14 EST 2019. Contains 330013 sequences. (Running on oeis4.)