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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, 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
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
KEYWORD
nonn,tabf,more
AUTHOR
N. J. A. Sloane, Jun 24 2017
STATUS
approved