%I #9 Aug 22 2017 20:53:11
%S 0,0,0,1,1,11,13,83,162,930,1369,13730,16421,124702,355793,1356781,
%T 2555043,25933814,32931815,283330733,720489755,3308255032,5763641923,
%U 60874698532,93543112676,600086810852
%N Number of step cyclic shifted sequence structures 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. 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 A056431(n)-A056430(n).
%Y Column 4 of A288627.
%Y Cf. A056417.
%K nonn
%O 1,6
%A _Marks R. Nester_