A121859 - OEIS

%I #7 Jul 22 2013 15:23:20

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

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

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

%C a(17) > 25000. - _Robert Price_, Jul 22 2013

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

%Y Cf. A091415, A002982.

%K nonn

%O 1,2

%A _Alexander Adamchuk_, Sep 10 2006

%E a(12)-a(16) from _Robert Price_, Jul 22 2013