The On-Line Encyclopedia of Integer Sequences (OEIS)

A325262 revision #4

A325262

Number of integer partitions of n whose omega-sequence does not cover an initial interval of positive integers.

0, 0, 0, 1, 1, 2, 6, 7, 12, 18, 29, 38, 58, 77, 110, 145, 198, 257, 345, 441, 576, 733, 942, 1184, 1503, 1875, 2352, 2914, 3620, 4454, 5493, 6716, 8221, 10001, 12167, 14723, 17816, 21459, 25836, 30988, 37139, 44365, 52956, 63022, 74934, 88873, 105296, 124469

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OFFSET

0,6

COMMENTS

The omega-sequence of an integer partition is the sequence of lengths of the multisets obtained by repeatedly taking the multiset of multiplicities until a singleton is reached. For example, the partition (32211) has chain of multisets of multiplicities {1,1,2,2,3} -> {1,2,2} -> {1,2} -> {1,1} -> {2}, so its omega-sequence is (5,3,2,2,1).

LINKS

Table of n, a(n) for n=0..47.

EXAMPLE

The a(3) = 1 through a(9) = 18 partitions:

(111) (1111) (2111) (222) (421) (431) (333)

(11111) (321) (2221) (521) (432)

(2211) (4111) (2222) (531)

(3111) (22111) (3311) (621)

(21111) (31111) (5111) (3222)

(111111) (211111) (22211) (6111)

(1111111) (32111) (22221)

(41111) (32211)

(221111) (33111)

(311111) (42111)

(2111111) (51111)

(11111111) (222111)

(321111)

(411111)

(2211111)

(3111111)

(21111111)

(111111111)

MATHEMATICA

normQ[m_]:=Or[m=={}, Union[m]==Range[Max[m]]];

omseq[ptn_List]:=If[ptn=={}, {}, Length/@NestWhileList[Sort[Length/@Split[#]]&, ptn, Length[#]>1&]];

Table[Length[Select[IntegerPartitions[n], !normQ[omseq[#]]&]], {n, 0, 30}]

CROSSREFS

Cf. A055932, A181819, A182850, A225486, A323014, A323023, A325250, A325251, A325261, A325277, A325285.

Integer partition triangles: A008284 (first omega), A116608 (second omega), A325242 (third omega), A325268 (second-to-last omega), A225485 or A325280 (frequency depth), A325249 (sum).

Sequence in context: A190121 A105329 A124319 * A334906 A078471 A127406

Adjacent sequences: A325259 A325260 A325261 * A325263 A325264 A325265

KEYWORD

nonn

AUTHOR

Gus Wiseman, Apr 23 2019

STATUS

editing