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A154886 Number of ways to partition n into reduced fractions i/j with j <= n. 4
1, 5, 51, 655, 20980, 578779, 46097340, 2889706132, 485416306983, 68334145684271, 24330218582223815, 3847311627258606534, 2716890193805515507433, 1270766589764097820833691, 2188031110546839992589840986, 1331298554328475793875243619997 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Robert Gerbicz, Table of n, a(n) for n = 1..43

EXAMPLE

a(2) = #{2, 3/2+1/2, 1+1, 1+1/2+1/2, 1/2+1/2+1/2+1/2} = 5.

MATHEMATICA

modifiedFarey[n_] := Union@ Flatten@ Table[a/b, {b, n}, {a, b*n}]; t[n_, k_] := Length@ IntegerPartitions[n, {k}, modifiedFarey@ n]; Plus @@@ Table[t[n, k], {n, 7, 7}, {k, n*(Plus @@ EulerPhi@ Range@n)}] (* Robert G. Wilson v, Aug 30 2010 *)

CROSSREFS

Cf. A154887, A119983, A143270.

Sequence in context: A180511 A245926 A190734 * A268138 A145162 A187235

Adjacent sequences:  A154883 A154884 A154885 * A154887 A154888 A154889

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jan 17 2009

EXTENSIONS

a(7) from Robert G. Wilson v, Aug 30 2010

a(8)-a(16) from Robert Gerbicz, Nov 19 2010

STATUS

approved

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Last modified October 16 20:55 EDT 2019. Contains 328103 sequences. (Running on oeis4.)