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