A121859 Numbers n such that n!*3^n - 1 is prime.

1, 2, 12, 20, 38, 45, 46, 105, 117, 143, 214, 1835, 2931, 7703, 11542, 19225

Offset: 1

Author

Alexander Adamchuk, Sep 10 2006

Keywords

• nonn

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

Crossrefs

Cf. A091415, A002982.

Programs

Mathematica

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

Extensions

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