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.

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

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