A140714 - OEIS

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A140714

Triangle read by rows: T(n,k) is the number of white corners of rank k in all 321-avoiding permutations of {1,2,...,n} (n>=2, 0<=k<=n-2; for definitions see the Eriksson-Linusson references).

1, 3, 1, 9, 5, 2, 28, 19, 12, 5, 90, 68, 51, 33, 14, 297, 240, 197, 150, 98, 42, 1001, 847, 735, 609, 466, 306, 132

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OFFSET

2,2

COMMENTS

Sum of entries in row n is 4^(n-2) (A000302).

T(n,0)=A000245(n-1).

T(n,n-2)=Cat(n-2)=A000108(n-2).

REFERENCES

K. Eriksson and S. Linusson. Combinatorics of Fulton's essential set. Duke Mathematical Journal 85(1):61-76, 1996.

LINKS

Table of n, a(n) for n=2..29.