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A056070 Number of 5-element ordered antichains on an unlabeled n-element set; T_1-hypergraphs with 5 labeled nodes and n hyperedges. 1
30, 2206, 56242, 766198, 7056249, 49662920, 286860862, 1422695104, 6246302316, 24810260818, 90593318410, 307833736038 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

COMMENTS

T_1-hypergraph is a hypergraph (not necessarily without empty hyperedges or multiple hyperedges) which for every ordered pair of distinct nodes has a hyperedge containing one but not the other node.

REFERENCES

V. Jovovic and G. Kilibarda, On the number of Boolean functions in the Post classes F^{mu}_8, Diskretnaya Matematika, 11 (1999), no. 4, 127-138 (translated in Discrete Mathematics and Applications, 9, (1999), no. 6)

V. Jovovic, G. Kilibarda, On enumeration of the class of all monotone Boolean functions, in preparation.

LINKS

Table of n, a(n) for n=4..15.

K. S. Brown, Dedekind's problem

FORMULA

a(n)=C(n + 31, 31) - 20*C(n + 23, 23) + 60*C(n + 19, 19) + 20*C(n + 17, 17) + 10*C(n + 16, 16) - 110*C(n + 15, 15) - 120*C(n + 14, 14) + 150*C(n + 13, 13) + 120*C(n + 12, 12) - 240*C(n + 11, 11) + 20*C(n + 10, 10) + 240*C(n + 9, 9) + 40*C(n + 8, 8) - 205*C(n + 7, 7) + 60*C(n + 6, 6) - 210*C(n + 5, 5) + 210*C(n + 4, 4) + 50*C(n + 3, 3) - 100*C(n + 2, 2) + 24*C(n + 1, 1).

CROSSREFS

Cf. A051113 for 5-element (unordered) antichains on a labeled n-element set, A056005.

Sequence in context: A092617 A295446 A056093 * A301377 A054647 A061162

Adjacent sequences:  A056067 A056068 A056069 * A056071 A056072 A056073

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Goran Kilibarda, Zoran Maksimovic, Jul 26 2000

STATUS

approved

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Last modified May 23 01:37 EDT 2019. Contains 323507 sequences. (Running on oeis4.)