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 A056404 #6 Aug 22 2017 20:53:11 %S A056404 1,1,3,9,17,111,156,1099,3072,21789,42334,528487,859501,8546878, %T A056404 31968376,159715435,398048505,5303677376,8835749346,99411964817, %U A056404 331215913868,1987084087016,4515860983384,62095480510303 %N A056404 Number of primitive (aperiodic) step shifted (decimated) sequence structures using a maximum of five different symbols. %C A056404 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A056404 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 A056404 Sum mu(d)*A056394(n/d) where d|n. %Y A056404 Cf. A056384. %K A056404 nonn %O A056404 1,3 %A A056404 _Marks R. Nester_