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A140714
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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).
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0
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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
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2,2
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COMMENTS
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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).
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REFERENCES
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K. Eriksson and S. Linusson. Combinatorics of Fulton's essential set. Duke Mathematical Journal 85(1):61-76, 1996.
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LINKS
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Table of n, a(n) for n=2..29.
K. Eriksson and S. Linusson, The size of Fulton's essential set, Electronic J. Combinatorics, Vol. 2, #R6, 1995.
K. Eriksson and S. Linusson, Combinatorics of Fulton's essential set, ResearchGate, 1998.
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EXAMPLE
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Triangle starts:
1;
3,1;
9,5,2;
28,19,12,5;
90,68,51,33,14;
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CROSSREFS
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Cf. A000302, A000245, A000108, A140713.
Sequence in context: A112626 A050155 A270236 * A112932 A337680 A077895
Adjacent sequences: A140711 A140712 A140713 * A140715 A140716 A140717
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KEYWORD
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nonn,tabl,more
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AUTHOR
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Emeric Deutsch, May 29 2008
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STATUS
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approved
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