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 A056507 Number of periodic palindromic structures using a maximum of six different symbols. 4
 1, 1, 2, 2, 5, 5, 13, 15, 41, 52, 144, 203, 577, 876, 2587, 4111, 12589, 20648, 65519, 109299, 356613, 601492, 2005545, 3403127, 11522829, 19628064, 67183531, 114700315, 395497312, 676207628, 2343265049, 4010090463, 13942486653, 23874362200, 83192239491, 142508723651 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure. 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 = 0..200 FORMULA a(n) = Sum_{k=1..6} A285012(n, k) for n > 0. - Andrew Howroyd, Oct 01 2019 CROSSREFS Cf. A056471, A285012. Sequence in context: A321395 A056505 A056506 * A285013 A095014 A129996 Adjacent sequences:  A056504 A056505 A056506 * A056508 A056509 A056510 KEYWORD nonn AUTHOR EXTENSIONS Corrected by T. D. Noe, Oct 25 2006 a(0)=1 prepended and terms a(16) and beyond from Andrew Howroyd, Oct 01 2019 STATUS approved

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Last modified October 21 19:19 EDT 2019. Contains 328308 sequences. (Running on oeis4.)