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 A056441 #6 Aug 22 2017 20:53:12 %S A056441 1,1,2,5,6,29,28,142,242,1222,1664,15935,18198,134452,376424,1415060, %T A056441 2634596,26534337,33499358,287001476,727425470,3332039278,5794658930, %U A056441 61120838930,93825569002,601444720052 %N A056441 Number of primitive (period n) step cyclic shifted sequence structures using a maximum of four different symbols. %C A056441 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 A056441 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 A056441 sum mu(d)*A056431(n/d) where d|n. %Y A056441 Cf. A056421. %K A056441 nonn %O A056441 1,3 %A A056441 _Marks R. Nester_