OFFSET
1,5
COMMENTS
a(n)! < n for all n. Thus a(n) = 0 is definite.
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..10000
EXAMPLE
11 - 1! = 10 is not prime.
11 - 2! = 9 is not prime.
11 - 3! = 5 is prime. Thus a(11) = 3.
PROG
(PARI)
a(n)=for(k=1, n, if(ispseudoprime(n-k!), return(k)))
vector(150, n, a(n))
CROSSREFS
KEYWORD
nonn
AUTHOR
Derek Orr, Jul 30 2014
STATUS
approved