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 A056431 #10 Aug 22 2017 20:53:11
%S A056431 1,2,3,7,7,33,29,149,245,1230,1665,15973,18199,134482,376433,1415209,
%T A056431 2634597,26534612,33499359,287002711,727425501,3332040944,5794658931,
%U A056431 61120855045,93825569009,601444738252
%N A056431 Number of step cyclic shifted sequence structures using a maximum of four different symbols.
%C A056431 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 A056431 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 Use de Bruijn's generalization of Polya's enumeration theorem as discussed in reference.
%F A056431 a(n) = Sum_{k=1..4} A288627(n, k). - _Andrew Howroyd_, Jun 13 2017
%Y A056431 Cf. A056412, A288627.
%K A056431 nonn
%O A056431 1,2
%A A056431 _Marks R. Nester_