%I #6 Aug 22 2017 20:53:11
%S 1,1,3,9,16,102,130,800,1889,11089,17598,179255,233448,1865925,
%T 5603767,22468480,44744046,477260541,636308684,5732446015,15272176563,
%U 73301037291,133274359128,1466413083360
%N Number of primitive (aperiodic) step shifted (decimated) sequence structures using a maximum of four different symbols.
%C See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure.
%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)*A056393(n/d) where d|n.
%Y Cf. A056383.
%K nonn
%O 1,3
%A _Marks R. Nester_