OFFSET
1,3
COMMENTS
The terms beyond a(3), found by PrimeForm, produce probable primes of lengths 24, 199, 1747 and 16474 digits. As both (8!)! and 2*((8!)!) each have the same number of digits, a(8) will correspond to a 168187-digit prime (by Bertrand's Postulate). For all n, if k > 1, then k >= nextprime(n!). As (8!)!+1 is composite, a(8) >= 40343.
EXAMPLE
a(3) = 7 as (3!)! + 7 = 6! + 7 = 720 + 7 = 727 is the smallest prime larger than (3!)!.
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Rick L. Shepherd, Oct 04 2007
STATUS
approved