id:A114338 - OEIS Search Results

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Number of positive divisors of n!! (double factorial = A006882(n)).

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1, 2, 2, 4, 4, 10, 8, 16, 16, 36, 32, 66, 64, 144, 120, 192, 240, 340, 480, 570, 864, 1200, 1728, 1656, 2880, 3456, 4320, 5616, 8640, 9072, 17280, 10752, 28800, 22176, 46080, 30240, 92160, 62208, 152064, 84240, 304128, 128000, 608256, 201600 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`a(n) = sigma_0(n!!) = tau(n!!).`
	EXAMPLE	`a(5)=4 since 5!!=15 and the divisors are 1, 3, 5 and 15.`
	MATHEMATICA	`DivisorSigma[0, Range[50]!! ]`
	CROSSREFS	`Cf. A027423, A006882.` `Sequence in context: A035054 A099537 A109525 this_sequence A133406 A005293 A057784` `Adjacent sequences: A114335 A114336 A114337 this_sequence A114339 A114340 A114341`
	KEYWORD	`easy,nonn`
	AUTHOR	`Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 07 2006`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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