A360068 - OEIS

A360068

Number of integer partitions of n such that the parts have the same mean as the multiplicities.

1, 1, 0, 0, 1, 0, 0, 0, 2, 1, 0, 0, 6, 0, 0, 0, 6, 0, 7, 0, 1, 0, 0, 0, 0, 90, 0, 63, 0, 0, 0, 0, 11, 0, 0, 0, 436, 0, 0, 0, 0, 0, 0, 0, 0, 2157, 0, 0, 240, 1595, 22, 0, 0, 0, 6464, 0, 0, 0, 0, 0, 0, 0, 0, 11628, 4361, 0, 0, 0, 0, 0, 0, 0, 12927, 0, 0, 621, 0

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OFFSET

0,9

COMMENTS

Note that such a partition cannot be strict for n > 1.

Conjecture: If n is squarefree, then a(n) = 0.

LINKS

Table of n, a(n) for n=0..76.

EXAMPLE

The n = 1, 4, 8, 9, 12, 16, 18 partitions (D=13):

(1) (22) (3311) (333) (322221) (4444) (444222)

(5111) (332211) (43222111) (444411)

(422211) (43321111) (552222)

(522111) (53221111) (555111)

(531111) (54211111) (771111)

(621111) (63211111) (822222)

(D11111)

For example, the partition (4,3,3,3,3,3,2,2,1,1) has mean 5/2, and its multiplicities (1,5,2,2) also have mean 5/2, so it is counted under a(20).

MATHEMATICA

Table[Length[Select[IntegerPartitions[n], Mean[#]==Mean[Length/@Split[#]]&]], {n, 0, 30}]

CROSSREFS

These partitions are ranked by A359903, for prime factors A359904.

Positions of positive terms are A360070.

A000041 counts partitions, strict A000009.

A058398 counts partitions by mean, see also A008284, A327482.

A088529/A088530 gives mean of prime signature (A124010).

A326567/A326568 gives mean of prime indices (A112798).

A360069 counts partitions whose multiplicities have integer mean.

Cf. A067340, A067538, A082550, A240219, A316313, A327475, A349156, A359893, A359897, A359905.

Sequence in context: A057150 A185663 A262125 * A105868 A371568 A267163

Adjacent sequences: A360065 A360066 A360067 * A360069 A360070 A360071

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 27 2023

STATUS

approved