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%I #25 Oct 14 2018 03:56:57
%S 1,2,3,4,5,8,13,18,27,45,70,111,180,308,491,790,1319,2231,3747,6396,
%T 10761,18291,30947,52611,89157,152514,260277,445869,762919,1307688,
%U 2246172,3857544,6641424,11440114,19728780,34057328,58834623,101709014,176009032,304766442
%N Number of primes of the form x^4 + 1 less than 10^n.
%C 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.
%H Chai Wah Wu, <a href="/A214452/b214452.txt">Table of n, a(n) for n = 1..46</a>
%e a(3) = 3 because the only primes of the form x^4 + 1 < 10^3 are the primes: 2, 17, 257.
%o (PARI) a(n) = sum(k=1,(10^n-1)^(1/4), isprime(k^4+1))
%Y Cf. A083844, A214454, A214455.
%K nonn
%O 1,2
%A _Henryk Dabrowski_, Jul 18 2012
%E More terms from _Henryk Dabrowski_, Jul 26 2012
%E a(37)-a(40) from _Chai Wah Wu_, Oct 13 2018
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