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A056320 Number of primitive (aperiodic) reversible strings with n beads using exactly four different colors. 1
0, 0, 0, 12, 120, 780, 4212, 20412, 93360, 409260, 1749780, 7338000, 30394560, 124700928, 508291692, 2061586800, 8332140720, 33585682920, 135116412660, 542785390680, 2178110585388, 8733343485120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

A string and its reverse are considered to be equivalent.

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..22.

FORMULA

sum mu(d)*A056311(n/d) where d|n.

CROSSREFS

Cf. A056315.

Sequence in context: A001816 A133386 A305624 * A056311 A009050 A067358

Adjacent sequences:  A056317 A056318 A056319 * A056321 A056322 A056323

KEYWORD

nonn

AUTHOR

Marks R. Nester

STATUS

approved

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Last modified July 21 19:25 EDT 2019. Contains 325199 sequences. (Running on oeis4.)