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A114338 Number of positive divisors of n!! (double factorial = A006882(n)). 0
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; refs; listen; history; internal format)
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 * A170831 A133406 A005293

Adjacent sequences:  A114335 A114336 A114337 * A114339 A114340 A114341

KEYWORD

easy,nonn

AUTHOR

Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 07 2006

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Last modified February 17 19:13 EST 2012. Contains 206085 sequences.