OFFSET
1,1
COMMENTS
Next term a(20)=2493493447.
EXAMPLE
f(n)=n^2+n+41
n=1, p=16355881:
f(p)=267514859642083 prime,
f(f(p))=71564200129323635349724221013, prime
f(f(f(p))) =5121434740149885026514070854977073540325438908499394967223, prime
f(f(f(f(p)))) prime, f(f(f(f(f(p))))) prime, f(f(f(f(f(f(p)))))) not-prime.
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jan 31 2009
STATUS
approved