A288558 Irregular triangle read by rows: distribution of inversion numbers over the set of permutations of the multiset {1,1,2,2,3,3,...,n,n} avoiding the pattern 123.

1, 1, 1, 2, 1, 1, 0, 0, 0, 0, 3, 3, 6, 7, 9, 7, 5, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 4, 6, 15, 18, 28, 35, 44, 47, 49, 42, 31, 18, 9, 3, 1

Offset

1,4

Links

Table of n, a(n) for n=1..44.

A. M. Baxter, Algorithms for Permutation Statistics, Ph. D. Dissertation, Rutgers University, May 2011. See Table 4.1.

Example

Triangle begins:
1,
1,1,2,1,1,
0,0,0,0,3,3,6,7,9,7,5,2,1,
0,0,0,0,0,0,0,0,1,1,4,6,15,18,28,35,44,47,49,42,31,18,9,3,1,
...

Crossrefs

Row sums give A220097.

Sequence in context: A339659 A338971 A244600 * A362831 A269241 A086013

Adjacent sequences: A288555 A288556 A288557 * A288559 A288560 A288561

Keyword

nonn,tabf,more

Author

N. J. A. Sloane, Jun 24 2017

Status

approved