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 A056510 Number of periodic palindromic structures of length n using exactly four different symbols. 3
 0, 0, 0, 0, 0, 1, 1, 7, 10, 43, 65, 220, 350, 1059, 1701, 4803, 7770, 21105, 34105, 90248, 145750, 379391, 611501, 1573432, 2532530, 6465473, 10391745, 26379908, 42355950, 107091559, 171798901, 433093459, 694337290, 1746630985, 2798806985, 7029341790, 11259666950 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 REFERENCES 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] LINKS Andrew Howroyd, Table of n, a(n) for n = 1..200 FORMULA a(n) = A056505(n) - A056504(n). Inverse Moebius transform of A056521. - Andrew Howroyd, Oct 01 2019 EXAMPLE For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. CROSSREFS Column 4 of A285012. Cf. A056473, A056504, A056505, A056521. Sequence in context: A258284 A099579 A056521 * A013398 A013493 A166661 Adjacent sequences:  A056507 A056508 A056509 * A056511 A056512 A056513 KEYWORD nonn AUTHOR EXTENSIONS Corrected by T. D. Noe, Oct 25 2006 a(17)-a(30) from Andrew Howroyd, Apr 07 2017 Terms a(31) and beyond from Andrew Howroyd, Oct 01 2019 STATUS approved

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Last modified April 3 13:32 EDT 2020. Contains 333197 sequences. (Running on oeis4.)