%I #6 Aug 22 2017 20:53:11
%S 0,0,0,3,12,136,204,1434,3520,20688,31956,317374,390364,2973332,
%T 8504708,32469954,61276740,622084744,790198476,6798276744,17290257884,
%U 79394924652,138325216092,1460955163540
%N Number of primitive (period n) step cyclic shifted sequences using exactly four 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)*A056417(n/d) where d|n.
%Y Cf. A056421.
%K nonn
%O 1,4
%A _Marks R. Nester_
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