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 A056392 #10 Aug 22 2017 20:53:10
%S A056392 1,2,4,10,14,70,68,332,577,2510,2980,23372,22218,133150,300964,909382,
%T A056392 1345634,10767202,10762820,72957100,145362932,523029526,713213956,
%U A056392 5893709440,7060765733,35303782550
%N A056392 Number of step shifted (decimated) sequence structures using a maximum of three different symbols.
%C A056392 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure.
%D A056392 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 A056392 Use de Bruijn's generalization of Polya's enumeration theorem as discussed in reference.
%F A056392 a(n) = Sum_{k=1..3} A288620(n, k). - _Andrew Howroyd_, Jun 13 2017
%Y A056392 Cf. A056372, A288620.
%K A056392 nonn
%O A056392 1,2
%A A056392 _Marks R. Nester_