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%I #10 Oct 21 2021 10:46:38
%S 1,2,14,186,2880,50450,952854,19003474,394394880,8439756660,
%T 185033201150,4137181680698,94020326259264,2166105078791446,
%U 50489825369325118,1188777328563863850,28236363841594782720,675879582290807439794,16289254212695836475436
%N Number of Lyndon words (aperiodic necklaces) with 3n beads of 3 colors, n beads of each color.
%H <a href="/index/Lu#Lyndon">Index entries for sequences related to Lyndon words</a>
%F a(n) = 1/(3n) * Sum_{d|n} mu(n/d) * (3d)! / d!^3, a(0) = 1.
%F a(n) = A029808(n)*2 = A074651(n)/3.
%Y Cf. A029808, A074651, A022553 (2n of 2 colors), A074656 (4n of 4 colors).
%K nonn
%O 0,2
%A _Christian G. Bower_, Aug 29 2002
%E a(0)=1 prepended by _Alois P. Heinz_, Aug 24 2015