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A093593 n! times sum of Farey fractions of order n. 2
1, 3, 15, 84, 660, 4680, 47880, 463680, 5261760, 59875200, 858211200, 11256537600, 183697113600, 2833294464000, 47730114432000, 847372990464000, 17250840262656000, 329722245844992000, 7359528574734336000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..19.

Eric Weisstein's World of Mathematics, Farey Sequence..

EXAMPLE

Multiplication of n-th-order positive Farey fractions by n! gives the integer sequence A002088(n), for n>=1. Arrange them in rows:

1

1 2

2 3 4 6

6 8 12 16 18 24

The sum over row 4 is a(4)=84.

MATHEMATICA

Farey[n_] := Union[ Flatten[ Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; Table[n!Plus @@ Farey[n], {n, 0, 20}] (* Robert G. Wilson v, Apr 06 2004 *)

CROSSREFS

Cf. A002088, A092824, A093594.

Sequence in context: A005809 A067122 A202336 * A212201 A011900 A118342

Adjacent sequences:  A093590 A093591 A093592 * A093594 A093595 A093596

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 03 2004

EXTENSIONS

More terms from Robert G. Wilson v, Apr 06 2004

STATUS

approved

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Last modified April 18 22:08 EDT 2019. Contains 322237 sequences. (Running on oeis4.)