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%I #20 Apr 20 2024 02:14:42
%S 0,0,0,0,0,0,0,0,0,0,0,0,0,1,27,170,1436,8835,44993,196391,762963,
%T 2714473,8939435
%N Number of nine-prime Carmichael numbers less than 10^n.
%H Claude Goutier, <a href="http://www-labs.iro.umontreal.ca/~goutier/OEIS/A055553/">Text file readme.text summarizing enumeration of Carmichael numbers up to 10^22</a>.
%H Claude Goutier, <a href="/A055553/a055553.txt">Text file readme.text summarizing enumeration of Carmichael numbers up to 10^22</a>. [Local copy, with permission]
%H R. G. E. Pinch, <a href="http://s369624816.websitehome.co.uk/rgep/p82.pdf">The Carmichael numbers up to 10^21</a>, Proceedings of Conference on Algorithmic Number Theory 2007.
%H R. G. E. Pinch, <a href="http://s369624816.websitehome.co.uk/rgep/p82p.pdf">The Carmichael numbers up to 10^21, Poster, Proceedings of Conference on Algorithmic Number Theory 2007.
%e The smallest Carmichael number with 9 prime factors is 9746347772161 = 7*11*13*17*19*31*37*41*641, so a(13)=1..
%Y For k-prime Carmichael numbers up to 10^n for k = 3,4,...,11, see A132195, A174612, A174613, A174614, A174615, A174616, A174617, A299710, A299711.
%Y Cf. A002997, A006931, A055553.
%K nonn,more
%O 0,15
%A _Michel Lagneau_, Mar 23 2010
%E a(22) from _Claude Goutier_ added by _Amiram Eldar_, Apr 19 2024