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Search: id:A163435
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| A163435 |
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Number of different fixed (possibly) disconnected pentominoes bounded tightly by an n*n square |
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+0
3
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| 0, 0, 102, 1792, 11550, 46848, 144550, 371712, 838782, 1715200, 3247398, 5779200, 9774622, 15843072, 24766950, 37531648, 55357950, 79736832, 112466662, 155692800, 211949598, 284204800, 375906342, 491031552, 634138750, 810421248
(list; graph; listen)
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OFFSET
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1,3
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FORMULA
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a(n)=2/3*n^2*(n-2)^2*(5n^2-10n+2), n>1
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EXAMPLE
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a(3)=102: there are 102 rotations of the 19 free (possibly) disconnected pentominoes bounded tightly by a 3*3 square; these include the F, T, V, W, X and Z (connected) pentominoes and 13 strictly disconnected free pentominoes
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CROSSREFS
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Cf. A162675, A163434, A163437
Sequence in context: A158127 A151964 A088805 this_sequence A030512 A097725 A129751
Adjacent sequences: A163432 A163433 A163434 this_sequence A163436 A163437 A163438
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KEYWORD
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nonn
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AUTHOR
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David Bevan (dbevan(AT)emtex.com), Jul 28 2009
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