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A124441
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a(n) = product{1<=k<=n/2, GCD(k,n)=1} k.
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4
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1, 1, 1, 1, 2, 1, 6, 3, 8, 3, 120, 5, 720, 15, 56, 105, 40320, 35, 362880, 189, 3200, 945, 39916800, 385, 9580032, 10395, 3203200, 19305, 87178291200, 1001, 1307674368000, 2027025, 65228800, 2027025, 4839284736, 85085
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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COMMENTS
| A124441(n) divides A001783(n). - M. F. Hasler, Jul 23 2011
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FORMULA
| A124441(n) = A001783(n)/A124442(n). - M. F. Hasler, Jul 23 2011
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EXAMPLE
| The positive integers which are <= 9/2 and which are coprime to 9 are 1, 2 and 4. So a(9) = 1*2*4 = 8.
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MAPLE
| a:=proc(n) local b, k: b:=1: for k from 1 to floor(n/2) do if gcd(k, n)=1 then b:=b*k else b:=b fi od: b; end: seq(a(n), n=1..41); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 03 2006
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MATHEMATICA
| f[n_] := Times @@ Select[Range[Floor[n/2]], GCD[ #, n] == 1 &]; Table[f[n], {n, 36}] (*Chandler*)
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PROG
| (PARI) A124441(n)=prod(k=2, n\2, k^(gcd(k, n)==1)) \\ - M. F. Hasler, Jul 23 2011
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CROSSREFS
| Cf. A124442.
Cf. A001783.
Sequence in context: A100014 A062566 A126265 * A026191 A050137 A086111
Adjacent sequences: A124438 A124439 A124440 * A124442 A124443 A124444
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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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