OFFSET
1,1
FORMULA
a(n) = A049433(n)-1 because n!-(n-1)!-1 = (n-1)*(n-1)!-1.
MATHEMATICA
Select[Range[2600], PrimeQ[#(#!)-1]&] (* Because a(22) generates a 7524 digit number to be tested for primality, the program takes a long time to run. *) (* Harvey P. Dale, May 27 2014 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Jan 15 2004
EXTENSIONS
More terms from Farideh Firoozbakht, Oct 31 2004
a(23)-a(24) using A049433 from Michel Marcus, May 29 2014
STATUS
approved