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A124740 a(n) = product of those positive integers which are coprime to both n and n+1 and which are <= n. 5
1, 1, 1, 3, 1, 5, 15, 35, 7, 189, 35, 385, 1485, 143, 1001, 2027025, 5005, 85085, 459459, 46189, 20995, 1249937325, 1616615, 7436429, 324342711, 71504125, 132793375, 1452095555625, 7436429, 215656441, 6190283353629375, 75969882625 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

The positive integers which are coprime to 8 and which are <= 8 are 1,3,5,7. The positive integers which are coprime to 9 and which are <= 9 are 1, 2,4,5,7,8. The integers in both these sequences (1,5,7) are multiplied to get a(8) = 35.

MATHEMATICA

f[n_] := Times @@ Select[Range[n], GCD[n, # ] == GCD[n + 1, # ] == 1 &]; Table[f[n], {n, 33}] (* Ray Chandler, Nov 10 2006 *)

CROSSREFS

Cf. A057475, A124738, A124739, A124741.

Sequence in context: A125053 A291665 A181836 * A347556 A338172 A104053

Adjacent sequences:  A124737 A124738 A124739 * A124741 A124742 A124743

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 06 2006

EXTENSIONS

Extended by Ray Chandler, Nov 10 2006

STATUS

approved

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Last modified May 28 22:08 EDT 2022. Contains 354122 sequences. (Running on oeis4.)