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A263857 Triangle read by rows: T(n,k) (n>=0, k>=n+1) is the number of posets with n elements and k antichains. 0
1, 1, 1, 1, 1, 2, 1, 0, 1, 1, 3, 3, 2, 3, 2, 0, 1, 0, 0, 0, 1, 1, 4, 6, 6, 9, 8, 7, 4, 5, 2, 2, 2, 3, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

COMMENTS

Row sums give A000112.

LINKS

Table of n, a(n) for n=0..47.

FindStat - Combinatorial Statistic Finder, The number of antichains of a poset.

EXAMPLE

Triangle begins:

1,

1,

1,1,

1,2,1,0,1,

1,3,3,2,3,2,0,1,0,0,0,1,

1,4,6,6,9,8,7,4,5,2,2,2,3,0,2,0,0,0,1,0,0,0,0,0,0,0,1,

...

The two element poset with 2 incomparable elements x, y has 4 antichains: {}, {x}, {y}, and {x,y}. The two element poset with 2 comparable elements x, y has 3 antichains: {}, {x}, and {y}. So T(2,1) = 1 and T(2,2) = 1.

CROSSREFS

Cf. A000112.

Sequence in context: A083856 A081718 A290353 * A198062 A226690 A245683

Adjacent sequences:  A263854 A263855 A263856 * A263858 A263859 A263860

KEYWORD

nonn,tabf

AUTHOR

Christian Stump, Oct 28 2015

STATUS

approved

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Last modified February 23 23:15 EST 2018. Contains 299595 sequences. (Running on oeis4.)