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A092880
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Number of ordered 2-multiantichains on an n-set.
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4
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1, 2, 6, 26, 126, 602, 2766, 12266, 52926, 223802, 932526, 3844106, 15722526, 63936602, 258902286, 1045109546, 4209004926, 16921851002, 67945160046, 272554432586, 1092540156126, 4377129999002, 17529432313806, 70180474597226
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Let P(A) be the power set of an n-element set A and R be a relation on P(A) such that for all x, y of P(A), xRy if either 0) x is not a subset of y and y is not a subset of x, or 1) x equals y. Then a(n) = |R|. [From Ross La Haye (rlahaye(AT)new.rr.com), Mar 19 2009]
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REFERENCES
| Ross La Haye, Binary Relations on the Power Set of an n-Element Set, Journal of Integer Sequences, Vol. 12 (2009), Article 09.2.6. [From Ross La Haye (rlahaye(AT)new.rr.com), Mar 19 2009]
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FORMULA
| a(n) = 4^n-2*3^n+2*2^n.
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CROSSREFS
| Cf. A092881-A092884.
Sequence in context: A192403 A050890 A114710 * A192808 A034474 A123872
Adjacent sequences: A092877 A092878 A092879 * A092881 A092882 A092883
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KEYWORD
| nonn
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AUTHOR
| Goran Kilibarda, Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 10 2004
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