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Search: id:A114854
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| 1, 1, 1, 2, 3, 4, 8, 10, 20, 26, 51, 64, 128, 163, 326, 416, 834, 1067, 2148, 2755, 5559, 7147, 14449, 18613, 37696, 48638
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OFFSET
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1,4
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COMMENT
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This sequence is a second approximation of a double factorial analogue to Stirling's approximation to factorial. Note that a(n) is exact for n = 1, 2, 4.
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FORMULA
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a(n) = Floor[n^(n/2)/n!! ]. a(n) = Floor[Sqrt(A000312(n))/A006882(n)].
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EXAMPLE
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a(10) = Floor[(10^5)/3840] = Floor[26.0416667] = 26.
a(11) = Floor[(11^5.5)/10395] = Floor[51.3848715] = 51.
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CROSSREFS
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Cf. A000312, A006882, A055775.
Sequence in context: A005542 A037171 A127352 this_sequence A127279 A050727 A102951
Adjacent sequences: A114851 A114852 A114853 this_sequence A114855 A114856 A114857
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Feb 20 2006
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