This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A056444 #9 Aug 22 2017 20:53:12 %S A056444 0,1,1,2,2,5,4,10,9,22,14,78,36,124,180,343,260,1329,804,3732,4428, %T A056444 9742,8384,47364,33778,108292,138756,408244,331184,2251604,1155734 %N A056444 Number of primitive (period n) step cyclic shifted sequence structures using exactly two different symbols. %C A056444 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. Identical to A056439 for n>1. %D A056444 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 A056444 a(n) = A056439(n) - A000007(n-1). %Y A056444 Cf. A056424. %K A056444 nonn %O A056444 1,4 %A A056444 _Marks R. Nester_