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A056474
Number of palindromic structures using exactly five different symbols.
1
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 15, 15, 140, 140, 1050, 1050, 6951, 6951, 42525, 42525, 246730, 246730, 1379400, 1379400, 7508501, 7508501, 40075035, 40075035, 210766920, 210766920, 1096190550
OFFSET
1,11
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
stirling2( [(n+1)/2], 5).
G.f.: -x^9/((x-1)*(2*x-1)*(2*x+1)*(2*x^2-1)*(3*x^2-1)*(5*x^2-1)). [Colin Barker, Jul 24 2012]
MATHEMATICA
Table[StirlingS2[Floor[(n+1)/2], 5], {n, 40}] (* Harvey P. Dale, Dec 18 2012 *)
CROSSREFS
Sequence in context: A036379 A070920 A056484 * A219912 A240980 A134912
KEYWORD
nonn,easy
STATUS
approved