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A121859 Numbers n such that n!*3^n - 1 is prime. 2
1, 2, 12, 20, 38, 45, 46, 105, 117, 143, 214, 1835, 2931, 7703, 11542, 19225 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Corresponding primes of the form n!*3^n - 1 are a(n)!*3^a(n) - 1 ={2,17,254561089305599,8483004771271882804592639999,...}.

a(17) > 25000. - Robert Price, Jul 22 2013

LINKS

Table of n, a(n) for n=1..16.

MATHEMATICA

Do[f=n!*3^n-1; If[PrimeQ[f], Print[{n, f}]], {n, 1, 25000}]

CROSSREFS

Cf. A091415, A002982.

Sequence in context: A286683 A326238 A226399 * A145622 A266050 A291698

Adjacent sequences:  A121856 A121857 A121858 * A121860 A121861 A121862

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Sep 10 2006

EXTENSIONS

a(12)-a(16) from Robert Price, Jul 22 2013

STATUS

approved

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Last modified April 14 19:50 EDT 2021. Contains 342954 sequences. (Running on oeis4.)