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Search: id:A112578
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| A112578 |
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Number of indecomposable 3-D arrays of 0's and 1's with plane sums 2. |
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+0
3
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| 0, 8, 900, 359424, 370828800, 820150272000, 3435918974208000, 24957654229057536000, 294060698786444083200000, 5334667831784096818790400000, 42889554205720574193041408000000
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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P. J. Cameron and T. W. Mueller, Decomposable functors and the exponential principle, II, in preparation
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FORMULA
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a(1)=0, a(n) = (n!)^2*b(n)/2^n for n>1, where b(0)=1 and sum (n-1 choose k-1)*((2n-2k-1)!!)^2*b(k) = ((2n-1)!!)^2
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EXAMPLE
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a(2)=8: six pairs of opposite edges and two inscribed tetrahedra
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CROSSREFS
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Cf. A010796 (2-D case), A112579, A112580.
Sequence in context: A159707 A097818 A027725 this_sequence A112579 A064072 A146536
Adjacent sequences: A112575 A112576 A112577 this_sequence A112579 A112580 A112581
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KEYWORD
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nonn,easy
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AUTHOR
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Peter J. Cameron (p.j.cameron(AT)qmul.ac.uk), Sep 14 2005
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