OFFSET
1,3
COMMENTS
It is conjectured that there are infinitely many primes of the form x^8 + 1 (and thus this sequence never becomes constant), but this has not been proved.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..90 (terms 1..72 from Henryk Dabrowski)
EXAMPLE
a(16) = 3 because the only primes of the form x^8 + 1 < 10^16 are the primes: 2, 257, 65537.
PROG
(PARI) a(n) = sum(k=1, (10^n-1)^(1/8), isprime(k^8+1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Henryk Dabrowski, Jul 18 2012
EXTENSIONS
More terms from Henryk Dabrowski, Jul 28 2012
STATUS
approved