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A056281 Number of primitive (aperiodic) word structures of length n which contain exactly five different symbols. 1
0, 0, 0, 0, 1, 15, 140, 1050, 6951, 42524, 246730, 1379385, 7508501, 40074895, 210766919, 1096189500, 5652751651, 28958088579, 147589284710, 749206047975, 3791262568261, 19137821665325, 96416888184100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same 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

Table of n, a(n) for n=1..23.

FORMULA

a(n) = Sum_{n > 0, d|n} mu(d)*A000481(n/d).

CROSSREFS

Column 5 of A137651.

Cf. A056270.

Sequence in context: A133716 A035330 A002803 * A000481 A215765 A055903

Adjacent sequences:  A056278 A056279 A056280 * A056282 A056283 A056284

KEYWORD

nonn

AUTHOR

Marks R. Nester

STATUS

approved

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Last modified November 20 02:57 EST 2018. Contains 317371 sequences. (Running on oeis4.)