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 A056512 #25 Oct 01 2019 18:34:56 %S A056512 0,0,0,0,0,0,0,0,0,1,1,13,21,154,266,1488,2646,12857,22827,101485, %T A056512 179487,752647,1323652,5325239,9321312,36387288,63436373,242085648, %U A056512 420693273,1577871106,2734926558,10120485512,17505749898,64096921939,110687251039,401885424357 %N A056512 Number of periodic palindromic structures of length n using exactly six different symbols. %D A056512 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 A056512 Andrew Howroyd, <a href="/A056512/b056512.txt">Table of n, a(n) for n = 1..200</a> %F A056512 a(n) = A056507(n) - A056506(n). %F A056512 Inverse Moebius transform of A056523. - _Andrew Howroyd_, Oct 01 2019 %e A056512 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. %Y A056512 Column k=6 of A285012. %Y A056512 Cf. A056475, A056506, A056507, A056523. %K A056512 nonn %O A056512 1,12 %A A056512 _Marks R. Nester_ %E A056512 a(16)-a(26) from _Andrew Howroyd_, Apr 07 2017 %E A056512 Terms a(27) and beyond from _Andrew Howroyd_, Oct 01 2019