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A056304 Number of primitive (period n) n-bead necklace structures using exactly three different colored beads. 5
0, 0, 1, 2, 5, 17, 43, 124, 338, 941, 2591, 7234, 20125, 56407, 158349, 446492, 1262225, 3580330, 10181479, 29031306, 82968799, 237642659, 682014587, 1960974220, 5647919640, 16292741605, 47069104274, 136166647110, 394418199725, 1143821887473, 3320790074371 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
Turning over the necklace is not allowed. Colors may be permuted without changing the necklace 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
FORMULA
a(n) = Sum_{d|n} mu(d)*A056296(n/d), where mu = A008683 is the Möbius function.
a(n) = A002075(n) - A000048(n).
CROSSREFS
Column 3 of A107424.
Sequence in context: A300692 A076076 A136194 * A063106 A096295 A215580
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(28)-a(31) from Pontus von Brömssen, Aug 04 2024
STATUS
approved

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Last modified September 13 18:56 EDT 2024. Contains 375910 sequences. (Running on oeis4.)