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 A056401 #6 Aug 22 2017 20:53:11 %S A056401 1,1,2,4,5,16,13,42,49,133,107,600,351,1385,2164,4416,4115,22043, %T A056401 14601,67872,88360,209827,190745,1074534,839122,2796647,3730532, %U A056401 11275300,9587579,67193198,35792567 %N A056401 Number of primitive (aperiodic) step shifted (decimated) sequence structures using a maximum of two different symbols. %C A056401 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A056401 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 A056401 Sum mu(d)*A056391(n/d) where d divides n. %Y A056401 Cf. A056381. %K A056401 nonn %O A056401 1,3 %A A056401 _Marks R. Nester_