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A124442
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a(n) = product{n/2<=k<=n, GCD(k,n)=1} k.
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3
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1, 1, 2, 3, 12, 5, 120, 35, 280, 63, 30240, 77, 665280, 1287, 16016, 19305, 518918400, 2431, 17643225600, 46189, 14780480, 1322685, 28158588057600, 96577, 4317650168832, 58503375, 475931456000, 75218625, 3497296636753920000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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FORMULA
| A124442(n)=A001783(n)/A124441(n). - M. F. Hasler, Jul 23 2011
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EXAMPLE
| The integers which are >= 9/2 and are <= 9 and which are coprime to 9 are 5, 7 and 8. So a(9) = 5*7*8 = 280.
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MAPLE
| a:=proc(n) local b, k: b:=1: for k from ceil(n/2) to n do if gcd(k, n)=1 then b:=b*k else b:=b fi od: b; end: seq(a(n), n=1..33); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 03 2006
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MATHEMATICA
| f[n_] := Times @@ Select[Range[Ceiling[n/2], n], GCD[ #, n] == 1 &]; Table[f[n], {n, 30}] (*Chandler*)
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PROG
| (PARI) A124442(n)=prod(k=(n+1)\2, n-1, k^(gcd(k, n)==1)) \\ - M. F. Hasler, Jul 23 2011
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CROSSREFS
| Cf. A124441.
Sequence in context: A124444 A038610 A056819 * A088611 A137765 A104038
Adjacent sequences: A124439 A124440 A124441 * A124443 A124444 A124445
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet, Nov 01 2006.
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 03 2006
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