OFFSET
1,1
COMMENTS
a(18) must be greater than 2300. The sum of the first 1642 double factorials is a (probable) prime with 2286 digits.
Numbers corresponding to a(18)-a(23) are probable primes. - Farideh Firoozbakht, May 16 2010
EXAMPLE
5 belongs since 1!! + 2!! + 3!! + 4!! + 5!! = 29, a prime.
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 23 2006
EXTENSIONS
a(18)-a(23) from Farideh Firoozbakht, May 16 2010
STATUS
approved