id:A118644 - OEIS Search Results

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Number of distinct (n red, n blue, n green)-bead necklaces.

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1

2, 16, 188, 2896, 50452, 953056, 19003476, 394397776, 8439756848, 185033251616, 4137181680700, 94020327215200, 2166105078791448, 50489825388328608, 1188777328563914488, 28236363841989180496 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`Sum_{d\|n} ( phi(n/d)(3n Choose n)(2n Choose n) )/3n`
	MATHEMATICA	`f[n_] := Plus @@ (EulerPhi[n/# ]Binomial[3#, # ]Binomial[2#, # ] & /@ Divisors[n])/(3n)`
	CROSSREFS	`Cf. A003239.` `Sequence in context: A052606 A011553 A123898 this_sequence A006335 A051711 A012683` `Adjacent sequences: A118641 A118642 A118643 this_sequence A118645 A118646 A118647`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jacob Siehler (siehlerj(AT)wlu.edu), May 10 2006`

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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.

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