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 A056501 #12 Sep 29 2019 11:09:51
%S A056501 0,0,0,0,0,0,0,60,120,960,1800,9300,16800,71400,126000,480000,834120,
%T A056501 2968440,5103000,17354340,29607600,97566000,165528000,533264700,
%U A056501 901020120,2854995360,4809004080,15050445900,25292030400,78417321240,131542866000,404936052000
%N A056501 Number of primitive (period n) periodic palindromes using exactly five different symbols.
%D A056501 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 A056501 Andrew Howroyd, <a href="/A056501/b056501.txt">Table of n, a(n) for n = 1..200</a>
%F A056501 a(n) = Sum_{d|n} mu(d)*A056491(n/d).
%e A056501 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome.
%Y A056501 Column 5 of A327878.
%Y A056501 Cf. A056466, A056491.
%K A056501 nonn
%O A056501 1,8
%A A056501 _Marks R. Nester_
%E A056501 Terms corrected by _Andrew Howroyd_, Sep 28 2019