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A056354
Number of bracelet structures using a maximum of four different colored beads.
8
1, 1, 2, 3, 7, 11, 33, 73, 237, 703, 2433, 8309, 30108, 108991, 403262, 1497070, 5607437, 21076571, 79595990, 301492045, 1145560579, 4363503684, 16660204452, 63741248201, 244339646708, 938255682551, 3608668388957, 13900021844558, 53614340398327, 207062143625711
OFFSET
0,3
COMMENTS
Turning over will not create a new bracelet. Permuting the colors of the beads 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
FORMULA
Use de Bruijn's generalization of Polya's enumeration theorem as discussed in reference.
a(n) = Sum_{k=1..4} A152176(n, k) for n > 0. - Andrew Howroyd, Oct 25 2019
CROSSREFS
Sequence in context: A140108 A034295 A338320 * A072534 A056292 A106125
KEYWORD
nonn
EXTENSIONS
a(0)=1 prepended and terms a(26) and beyond from Andrew Howroyd, Oct 25 2019
STATUS
approved