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A114714
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Number of linear extensions of a 2 X 2 X n lattice.
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2
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1, 2, 48, 2452, 183958, 17454844, 1941406508, 242201554680, 32959299267334, 4801233680739724, 738810565910888784, 118929992674840615128, 19880920716640427983476, 3431624482227380273056728
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Comment from Nick Krempel (ndkrempel(AT)blueyonder.co.uk), Jul 08 2010: The additional terms were found using dynamic programming to count the maximal chains in the distributive lattice of order-preserving functions from the chain of length n to J(P), where J is the lattice of downsets of the poset P = 2x2.
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REFERENCES
| Stanley, R., Enumerative Combinatorics, Vol. 2, Prop. 7.10.3 and Vol. 1, Sec 3.5, Chains in Distributive Lattices.
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LINKS
| Nick Krempel, Table of n, a(n) for n=0..40
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CROSSREFS
| Cf. A114717.
Sequence in context: A119698 A112103 A177317 * A186416 A087085 A067626
Adjacent sequences: A114711 A114712 A114713 * A114715 A114716 A114717
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KEYWORD
| nonn,hard
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AUTHOR
| Mitch Harris (Harris.Mitchell (AT) mgh.harvard.edu), Dec 27, 2005
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EXTENSIONS
| More terms from Nick Krempel (ndkrempel(AT)blueyonder.co.uk), Jul 08 2010
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