%I #6 Aug 22 2017 20:53:11
%S 0,0,0,1,3,37,63,478,1316,8594,14619,155961,211231,1732844,5302820,
%T 21559430,43398413,466493982,625545865,5659491433,15126813702,
%U 72778010746,132561145173,1460519397614,2338565021379
%N Number of primitive (aperiodic) step shifted (decimated) sequence structures using exactly 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 A056403(n)-A056402(n).
%Y Cf. A056388.
%K nonn
%O 1,5
%A _Marks R. Nester_