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A162675
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Number of different fixed (possibly) disconnected pentominoes bounded (not necessarily tightly) by an n*n square
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4
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0, 0, 114, 2910, 26490, 145110, 582540, 1891764, 5263020, 13010580, 29297070, 61162530, 119933814, 223098330, 396734520, 678599880, 1121985720, 1800456264, 2813598090, 4293914310, 6415006290, 9401194110, 13538735364, 19188810300
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Fixed quasi-pentominoes.
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FORMULA
| a(n) = n*(n-1)*(n-2)*(n+1)*(5*n^4-10*n^3-7*n^2+12*n+6)/24
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EXAMPLE
| a(3)=114: there are 114 rotations of the 21 free (possibly) disconnected pentominoes bounded (not necessarily tightly) by an 3*3 square; these include the F, P, T, U, V, W, X and Z (connected) pentominoes and 13 strictly disconnected pentominoes.
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CROSSREFS
| Cf. A162674, A162676, A162677, A094172 (free quasi-pentominoes).
Sequence in context: A108344 A200551 A200891 * A112485 A199249 A199193
Adjacent sequences: A162672 A162673 A162674 * A162676 A162677 A162678
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KEYWORD
| nonn
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AUTHOR
| David Bevan (dbevan(AT)emtex.com), Jul 27 2009
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EXTENSIONS
| Example moved to correct section, and ref to free quasi-pentominoes added by David Bevan (dbevan(AT)emtex.com), Mar 05 2011
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