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 A288621 #8 Oct 15 2017 08:47:08 %S A288621 1,2,4,11,18,117,162,1205,3621,29271,68086,1069614,2305158,31825670, %T A288621 172974370,1311400891,5179123522,113680235941,324041807958, %U A288621 6466011855715,39572612670818,450671611457619,2006909406239780,55745145216877102,231929517217884081 %N A288621 Number of step shifted (decimated) sequence structures of length n using an infinite alphabet. %C A288621 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A288621 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] %o A288621 (PARI) \\ see A056391 for Polya enumeration functions %o A288621 a(n) = NonequivalentStructs(StepShiftPerms(n), n); \\ _Andrew Howroyd_, Oct 14 2017 %Y A288621 Row sums of A288620. %Y A288621 Cf. A056391, A056371, A288628. %K A288621 nonn %O A288621 1,2 %A A288621 _Andrew Howroyd_, Jun 11 2017