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 A056502 #10 Sep 29 2019 11:02:11
%S A056502 0,0,0,0,0,0,0,0,0,360,720,7920,15120,103320,191520,1048320,1905120,
%T A056502 9170280,16435440,72832680,129230640,541129320,953029440,3832179120,
%U A056502 6711344640,26192751480,45674188560,174286569240,302899156560,1136022947280,1969147121760
%N A056502 Number of primitive (period n) periodic palindromes using exactly six different symbols.
%D A056502 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 A056502 Andrew Howroyd, <a href="/A056502/b056502.txt">Table of n, a(n) for n = 1..200</a>
%F A056502 a(n) = Sum_{d|n} mu(d)*A056492(n/d).
%e A056502 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome.
%Y A056502 Column 6 of A327878.
%Y A056502 Cf. A056467, A056492.
%K A056502 nonn
%O A056502 1,10
%A A056502 _Marks R. Nester_
%E A056502 Terms a(28) and beyond from _Andrew Howroyd_, Sep 28 2019