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A095987
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a(n) = gcd(n!!, (n-1)!!) where n!! = A006882.
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1
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1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 15, 15, 45, 45, 315, 315, 315, 315, 2835, 2835, 14175, 14175, 155925, 155925, 467775, 467775, 6081075, 6081075, 42567525, 42567525, 638512875, 638512875, 638512875, 638512875, 10854718875, 10854718875, 97692469875, 97692469875
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OFFSET
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0,7
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COMMENTS
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Let f_n(m) be a multifactorial: for m = positive integer, f_n(m) = Product_{k=0..floor((m-1)/n)} (m - k*n). E.g., f_2(m) = m!!. f_n(0) is defined as 1.
a(2m) = a(2m+1) = the largest odd divisor of m! (which is A049606).
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LINKS
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MAPLE
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a:= n-> (d-> gcd(d(n), d(n-1)))(doublefactorial):
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MATHEMATICA
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f[n_] := GCD[n!!, (n - 1)!! ]; Table[ f[n], {n, 35}]
GCD@@#&/@Partition[Range[0, 40]!!, 2, 1] (* Harvey P. Dale, May 04 2015 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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