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A332639
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Number of integer partitions of n whose negated run-lengths are not unimodal.
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33
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0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 4, 7, 10, 17, 25, 36, 51, 75, 102, 143, 192, 259, 346, 462, 599, 786, 1014, 1309, 1670, 2133, 2686, 3402, 4258, 5325, 6623, 8226, 10134, 12504, 15328, 18779, 22878, 27870, 33762, 40916, 49349, 59457, 71394, 85679, 102394
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OFFSET
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0,11
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COMMENTS
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A sequence of positive integers is unimodal if it is the concatenation of a weakly increasing and a weakly decreasing sequence.
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LINKS
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EXAMPLE
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The a(8) = 1 through a(13) = 10 partitions:
(3221) (4221) (5221) (4331) (4332) (5332)
(32221) (6221) (5331) (6331)
(42221) (7221) (8221)
(322211) (43221) (43321)
(52221) (53221)
(322221) (62221)
(422211) (332221)
(422221)
(522211)
(3222211)
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MATHEMATICA
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unimodQ[q_]:=Or[Length[q]<=1, If[q[[1]]<=q[[2]], unimodQ[Rest[q]], OrderedQ[Reverse[q]]]]
Table[Length[Select[IntegerPartitions[n], !unimodQ[-Length/@Split[#]]&]], {n, 0, 30}]
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CROSSREFS
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The version for normal sequences is A328509.
The non-negated complement is A332280.
The non-negated version is A332281.
The complement is counted by A332638.
The case that is not unimodal either is A332640.
The Heinz numbers of these partitions are A332642.
The generalization to run-lengths of compositions is A332727.
Non-unimodal permutations are A059204.
Non-unimodal compositions are A115981.
Compositions whose negation is not unimodal are A332669.
Cf. A007052, A025065, A100883, A181819, A332282, A332578, A332579, A332641, A332670, A332671, A332726, A332742, A332744.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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