OFFSET
1,5
COMMENTS
It is conjectured that there are infinitely many primes of the form x^16 + 1 (and thus this sequence never becomes constant), but this has not been proved.
EXAMPLE
a(26) = 2 because the only primes or the form x^16 + 1 < 10^26 are the primes: 2, 65537.
PROG
(PARI) a(n) = sum(k=1, (10^n-1)^(1/16), isprime(k^16+1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Henryk Dabrowski, Jul 18 2012
STATUS
approved