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 A056403 #6 Aug 22 2017 20:53:11 %S A056403 1,1,3,9,16,102,130,800,1889,11089,17598,179255,233448,1865925, %T A056403 5603767,22468480,44744046,477260541,636308684,5732446015,15272176563, %U A056403 73301037291,133274359128,1466413083360 %N A056403 Number of primitive (aperiodic) step shifted (decimated) sequence structures using a maximum of four different symbols. %C A056403 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A056403 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 Sum mu(d)*A056393(n/d) where d|n. %Y A056403 Cf. A056383. %K A056403 nonn %O A056403 1,3 %A A056403 _Marks R. Nester_