1,5

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.

Table of n, a(n) for n=1..70.

a(26) = 2 because the only primes or the form x^16 + 1 < 10^26 are the primes: 2, 65537.

(PARI) a(n) = sum(k=1, (10^n-1)^(1/16), isprime(k^16+1))

Cf. A083844, A214452, A214454.

Sequence in context: A069926 A077429 A204553 * A060417 A097944 A037203

Adjacent sequences: A214452 A214453 A214454 * A214456 A214457 A214458

nonn

Henryk Dabrowski, Jul 18 2012

approved