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A056338 Number of primitive (aperiodic) reversible string structures with n beads using exactly four different colors. 1
0, 0, 0, 1, 6, 37, 183, 876, 3930, 17179, 73095, 306323, 1267266, 5198374, 21182337, 85910040, 347187210, 1399447578, 5629911015, 22616239535, 90754854843, 363890053582, 1458172596903, 5840531328120, 23385650196084 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

A string and its reverse are considered to be equivalent. Permuting the colors 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

Table of n, a(n) for n=1..25.

FORMULA

A056333(n)-A056332(n).

CROSSREFS

Column 4 of A276544.

Cf. A056320.

Sequence in context: A129552 A293800 A327611 * A056328 A156185 A057418

Adjacent sequences:  A056335 A056336 A056337 * A056339 A056340 A056341

KEYWORD

nonn

AUTHOR

Marks R. Nester

STATUS

approved

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Last modified April 16 17:01 EDT 2021. Contains 343050 sequences. (Running on oeis4.)