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 A214452 Number of primes of the form x^4 + 1 less than 10^n. 5
 1, 2, 3, 4, 5, 8, 13, 18, 27, 45, 70, 111, 180, 308, 491, 790, 1319, 2231, 3747, 6396, 10761, 18291, 30947, 52611, 89157, 152514, 260277, 445869, 762919, 1307688, 2246172, 3857544, 6641424, 11440114, 19728780, 34057328 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS It is conjectured that there are infinitely many primes of the form x^4 + 1 (and thus this sequence never becomes constant), but this has not been proved. LINKS EXAMPLE a(3) = 3 because the only primes of the form x^4 + 1 < 10^3 are the primes: 2, 17, 257. PROG (PARI) a(n) = sum(k=1, (10^n-1)^(1/4), isprime(k^4+1)) CROSSREFS Cf. A083844, A214454, A214455. Sequence in context: A182153 A230771 A065490 * A282500 A222106 A222107 Adjacent sequences:  A214449 A214450 A214451 * A214453 A214454 A214455 KEYWORD nonn AUTHOR Henryk Dabrowski, Jul 18 2012 EXTENSIONS More terms from Henryk Dabrowski, Jul 26 2012 STATUS approved

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