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Search: id:A092439
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| A092439 |
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Sequence arising from enumeration of domino tilings of Aztec Pillow-like regions. |
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+0
2
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| 0, 0, 6, 30, 140, 560, 2058, 7098, 23472, 75372, 237182, 735878, 2260596, 6896136, 20933778, 63325170, 191089112, 575626052, 1731858246, 5206059774, 15640198620, 46966732320, 140996664986, 423191320490, 1269993390720
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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A092439(n) = Entry n+2 in row n of (Sequence to be added #1).
A092439(n) = A046717(n+2)-2^(n+2)-(n+2)(2^(n+1)-1)+(n+1)^2.
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REFERENCES
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J. Propp, Enumeration of matchings: problems and progress, pp. 255-291 in L. J. Billera et al., eds, New Perspectives in Algebraic Combinatorics, Cambridge, 1999 (see Problem 13).
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LINKS
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J. Propp, Publications and Preprints
J. Propp, Enumeration of matchings: problems and progress, in L. J. Billera et al. (eds.), New Perspectives in Algebraic Combinatorics
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FORMULA
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a(n)=(3^(n+2)+(-1)^(n+2))/2-2^(n+2)-(n+2)(2^(n+1)-1)+(n+1)^2
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EXAMPLE
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a(3)=(3^5+(-1)^5)/2-2^5-5(2^4-1)+4^2=30.
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CROSSREFS
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Cf. A092437-A092443.
Sequence in context: A002920 A001334 A125316 this_sequence A082149 A002457 A137400
Adjacent sequences: A092436 A092437 A092438 this_sequence A092440 A092441 A092442
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KEYWORD
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easy,nonn
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AUTHOR
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Christopher Hanusa (chanusa(AT)math.washington.edu), Mar 24 2004
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