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A263489 Triangle read by rows: T(n,k) (n>=2, 1<=k<=n!) is the number of permutations of n whose inversion arrangement contains k regions. 0
1, 1, 1, 2, 0, 2, 0, 1, 1, 3, 0, 5, 0, 2, 0, 4, 0, 0, 0, 4, 0, 1, 0, 0, 0, 3, 0, 0, 0, 0, 0, 1, 1, 4, 0, 9, 0, 3, 0, 12, 0, 0, 0, 10, 0, 2, 0, 8, 0, 6, 0, 0, 0, 0, 0, 14, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 14, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 4, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,4

COMMENTS

Row sums give A000142, n >= 2.

LINKS

Table of n, a(n) for n=2..101.

FindStat - Combinatorial Statistic Finder, The number of regions of inversion arrangement of a permutation.

EXAMPLE

Triangle begins:

1,1,

1,2,0,2,0,1,

1,3,0,5,0,2,0,4,0,0,0,4,0,1,0,0,0,3,0,0,0,0,0,1,

...

CROSSREFS

Cf. A000142.

Sequence in context: A193779 A279048 A263485 * A238660 A174793 A245718

Adjacent sequences:  A263486 A263487 A263488 * A263490 A263491 A263492

KEYWORD

nonn,tabf

AUTHOR

Christian Stump, Oct 19 2015

STATUS

approved

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Last modified October 18 01:39 EDT 2021. Contains 348065 sequences. (Running on oeis4.)