Many excellent designs for a new banner were submitted. We will use the best of them in rotation.
1,3
Used PrimeForm to prove primality for n = 4166 (classical N-1 test) - David Radcliffe, May 28 2007
Table of n, a(n) for n=1..14.
n=5 is here because 2*5!+1=241 is a prime.
Select[Range[0, 400], PrimeQ[2*#! + 1] &] (* Vladimir Joseph Stephan Orlovsky, Feb 13 2012 *)
Cf. A051888.
Sequence in context: A002139 A140489 A193776 * A064688 A089891 A004689
Adjacent sequences: A051912 A051913 A051914 * A051916 A051917 A051918
nonn
Labos Elemer, Dec 18 1999
4166 from David Radcliffe, May 28 2007
approved