id:A056328 - OEIS Search Results

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Number of reversible string structures with n beads using exactly four different colors.

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0, 0, 0, 1, 6, 37, 183, 877, 3930, 17185, 73095, 306361, 1267266, 5198557, 21182343, 85910917, 347187210, 1399451545, 5629911015, 22616256721, 90754855026, 363890126677, 1458172596903, 5840531635357, 23385650196090 (list; graph; listen)

	OFFSET	`1,5`
	COMMENT	`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.`
	FORMULA	`A056323(n)-A001998(n-1).`
	CROSSREFS	`Cf. A056311.` `Sequence in context: A047670 A129552 A056338 this_sequence A156185 A057418 A001419` `Adjacent sequences: A056325 A056326 A056327 this_sequence A056329 A056330 A056331`
	KEYWORD	`nonn`
	AUTHOR	`Marks R. Nester (nesterm(AT)dpi.qld.gov.au)`

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Last modified December 8 08:31 EST 2009. Contains 170430 sequences.

AT&T Labs Research