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 A056408 #6 Aug 22 2017 20:53:11 %S A056408 0,0,0,1,3,37,63,478,1316,8594,14619,155961,211231,1732844,5302820, %T A056408 21559430,43398413,466493982,625545865,5659491433,15126813702, %U A056408 72778010746,132561145173,1460519397614,2338565021379 %N A056408 Number of primitive (aperiodic) step shifted (decimated) sequence structures using exactly four different symbols. %C A056408 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A056408 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 A056408 A056403(n)-A056402(n). %Y A056408 Cf. A056388. %K A056408 nonn %O A056408 1,5 %A A056408 _Marks R. Nester_