OFFSET
1,1
COMMENTS
a(1)-a(8) have been proved to correspond to primes. No other terms less than 10000. - Robert Price, May 19 2012
EXAMPLE
4 is in the sequence because 4!*4^4 - 1 = 6143 is prime.
MATHEMATICA
Do[If[PrimeQ[n^n*n!-1], Print[n]], {n, 700}]
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Farideh Firoozbakht, Jul 14 2003
EXTENSIONS
a(8) = 3243 from Robert Price, May 19 2012
STATUS
approved