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 A056510 #24 Oct 01 2019 18:32:38 %S A056510 0,0,0,0,0,1,1,7,10,43,65,220,350,1059,1701,4803,7770,21105,34105, %T A056510 90248,145750,379391,611501,1573432,2532530,6465473,10391745,26379908, %U A056510 42355950,107091559,171798901,433093459,694337290,1746630985,2798806985,7029341790,11259666950 %N A056510 Number of periodic palindromic structures of length n using exactly four different symbols. %D A056510 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 A056510 Andrew Howroyd, <a href="/A056510/b056510.txt">Table of n, a(n) for n = 1..200</a> %F A056510 a(n) = A056505(n) - A056504(n). %F A056510 Inverse Moebius transform of A056521. - _Andrew Howroyd_, Oct 01 2019 %e A056510 For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. %Y A056510 Column 4 of A285012. %Y A056510 Cf. A056473, A056504, A056505, A056521. %K A056510 nonn %O A056510 1,8 %A A056510 _Marks R. Nester_ %E A056510 Corrected by _T. D. Noe_, Oct 25 2006 %E A056510 a(17)-a(30) from _Andrew Howroyd_, Apr 07 2017 %E A056510 Terms a(31) and beyond from _Andrew Howroyd_, Oct 01 2019