%I #6 Aug 22 2017 20:53:11
%S 0,0,1,6,9,55,51,252,379,1491,1611,12236,10245,57057,121711,345888,
%T 474489,3589099,3397143,21983298,41570721,142617777,186027579,
%U 1476401628,1694455311,8146623393,15690140775
%N Number of primitive (period n) step cyclic shifted sequences using exactly three different symbols.
%C See A056371 for an explanation of step shifts. Under step cyclic shifts, abcde, bdace, bcdea, cdeab and daceb etc. are equivalent.
%D M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
%F sum mu(d)*A056416(n/d) where d|n.
%Y Cf. A056420.
%K nonn
%O 1,4
%A _Marks R. Nester_