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 A056475 Number of palindromic structures using exactly six different symbols. 1
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 21, 21, 266, 266, 2646, 2646, 22827, 22827, 179487, 179487, 1323652, 1323652, 9321312, 9321312, 63436373, 63436373, 420693273, 420693273, 2734926558, 2734926558, 17505749898, 17505749898, 110687251039, 110687251039 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,13 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 (1,20,-20,-155,155,580,-580,-1044,1044,720,-720). FORMULA a(n) = stirling2( [(n+1)/2], 6). G.f.: x^11/((x-1)*(2*x-1)*(2*x+1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)*(6*x^2-1)). [Colin Barker, Jul 24 2012] CROSSREFS Cf. A000770, A056471. Sequence in context: A246034 A220689 A056485 * A219913 A219401 A219449 Adjacent sequences:  A056472 A056473 A056474 * A056476 A056477 A056478 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified September 23 10:55 EDT 2021. Contains 347612 sequences. (Running on oeis4.)