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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
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]
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
KEYWORD
nonn,easy
STATUS
approved