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

Author

N. J. A. Sloane, Jun 24 2017

Keywords

• nonn
• tabf
• more

Examples

			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,
...
		

Links

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

Crossrefs

Row sums give A220097.