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 A056511 #22 Oct 01 2019 18:34:31 %S A056511 0,0,0,0,0,0,0,1,1,10,15,85,140,618,1050,4065,6951,24915,42525,145067, %T A056511 246730,814215,1379400,4446631,7508501,23798600,40075035,125436313, %U A056511 210766920,653517228,1096190550,3374555449,5652751651,17305633285,28958095545,88274142232 %N A056511 Number of periodic palindromic structures of length n using exactly five different symbols. %D A056511 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 A056511 Andrew Howroyd, <a href="/A056511/b056511.txt">Table of n, a(n) for n = 1..200</a> %F A056511 a(n) = A056506(n) - A056505(n). %F A056511 Inverse Moebius transform of A056522. - _Andrew Howroyd_, Oct 01 2019 %e A056511 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. %Y A056511 Column 5 of A285012. %Y A056511 Cf. A056474, A056505, A056506, A056522. %K A056511 nonn %O A056511 1,10 %A A056511 _Marks R. Nester_ %E A056511 a(17)-a(28) from _Andrew Howroyd_, Apr 07 2017 %E A056511 Terms a(29) and beyond from _Andrew Howroyd_, Oct 01 2019