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 A288620 #11 Oct 15 2017 08:46:47 %S A288620 1,1,1,1,2,1,1,5,4,1,1,5,8,3,1,1,19,50,37,9,1,1,13,54,63,26,4,1,1,47, %T A288620 284,479,299,83,11,1,1,51,525,1316,1183,454,82,8,1,1,139,2370,8597, %U A288620 10701,5761,1492,196,13,1,1,107,2872,14619,24736,17998,6429,1198,119,6,1 %N A288620 Triangle read by rows: T(n,k) = number of step shifted (decimated) sequence structures of length n using exactly k different symbols. %C A288620 See A056371 for an explanation of step shifts. Permuting the symbols will not change the structure. %D A288620 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] %H A288620 Andrew Howroyd, <a href="/A288620/b288620.txt">Table of n, a(n) for n = 1..1275</a> %e A288620 Triangle begins %e A288620 1; %e A288620 1, 1; %e A288620 1, 2, 1; %e A288620 1, 5, 4, 1; %e A288620 1, 5, 8, 3, 1; %e A288620 1, 19, 50, 37, 9, 1; %e A288620 1, 13, 54, 63, 26, 4, 1; %e A288620 1, 47, 284, 479, 299, 83, 11, 1; %e A288620 1, 51, 525, 1316, 1183, 454, 82, 8, 1; %e A288620 ... %o A288620 (PARI) \\ see A056391 for Polya enumeration functions %o A288620 T(n,k) = NonequivalentStructsExactly(StepShiftPerms(n), k); \\ _Andrew Howroyd_, Oct 14 2017 %Y A288620 Columns 2-6 are A056396, A056397, A056398, A056399, A056400. %Y A288620 Row sums are A288621. %Y A288620 Partial row sums include A056391, A056392, A056393, A056394, A056395. %Y A288620 Cf. A056371, A288627, A285522, A285548, A132191. %K A288620 nonn,tabl %O A288620 1,5 %A A288620 _Andrew Howroyd_, Jun 11 2017