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 A056470 Number of palindromic structures using a maximum of five different symbols. 5
 1, 1, 2, 2, 5, 5, 15, 15, 52, 52, 202, 202, 855, 855, 3845, 3845, 18002, 18002, 86472, 86472, 422005, 422005, 2079475, 2079475, 10306752, 10306752, 51263942, 51263942, 255514355, 255514355, 1275163905 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS 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 Index entries for linear recurrences with constant coefficients, signature (1,10,-10,-31,31,30,-30). FORMULA a(2n-1) = a(2n) = A056272(n). [R. J. Mathar, Nov 24 2010] G.f.: -x*(19*x^6-24*x^4+9*x^2-1) / ((x-1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [Colin Barker, Dec 05 2012] MATHEMATICA LinearRecurrence[{1, 10, -10, -31, 31, 30, -30}, {1, 1, 2, 2, 5, 5, 15}, 40] (* Harvey P. Dale, Dec 16 2017 *) CROSSREFS Cf. A056451. Sequence in context: A097438 A205482 A055879 * A056471 A164904 A188164 Adjacent sequences:  A056467 A056468 A056469 * A056471 A056472 A056473 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified October 17 06:08 EDT 2019. Contains 328106 sequences. (Running on oeis4.)