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 A056374 #18 Dec 10 2017 20:06:32
%S A056374 5,25,75,375,825,8125,13175,103125,327125,2445625,4884435,61640625,
%T A056374 101732425,1017323125,3816215625,19104609375,47683838325,635787765625,
%U A056374 1059638680675,11924780390625,39736963221875,238418603522125,541860418146375
%N A056374 Number of step shifted (decimated) sequences using a maximum of five different symbols.
%C A056374 See A056371 for an explanation of step shifts.
%D A056374 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 A056374 G. C. Greubel, <a href="/A056374/b056374.txt">Table of n, a(n) for n = 1..1000</a>
%H A056374 R. C. Titsworth, <a href="http://projecteuclid.org/euclid.ijm/1256059671">Equivalence classes of periodic sequences</a>, Illinois J. Math., 8 (1964), 266-270.
%F A056374 The cycle index is implicit in Titsworth.
%F A056374 Sequences A056372-A056375 fit a general formula, implemented in PARI/GP as follows: { a(m,n) = sum(k=1, n, if(gcd(k, n)==1, m^sumdiv(n, d, eulerphi(d)/znorder(Mod(k, d))), 0); ) / eulerphi(n) }. - _Max Alekseyev_, Nov 08 2007
%t A056374 a[m_, n_] := (1/EulerPhi[n])*Sum[If[GCD[k, n] == 1, m^DivisorSum[n, EulerPhi[#]/MultiplicativeOrder[k, #] &], 0], {k, 1, n}]; Table[a[5, n], {n, 1, 23}] (* _Jean-François Alcover_, Dec 04 2015 *)
%Y A056374 Cf. A056413.
%Y A056374 A row or column of A132191.
%K A056374 nonn
%O A056374 1,1
%A A056374 _Marks R. Nester_
%E A056374 More terms from _Max Alekseyev_, Nov 08 2007