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A159295
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Number of ways that a tile in the form of a strip of n congruent regular hexagons stuck together on successive parallel edges can be surrounded by one layer of copies of itself in a plane. Ways that differ by rotation or reflection are not counted as different. The surrounded tile is the exact surrounded region.
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1
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1, 721, 1842, 4025, 7856, 14124, 23936, 38654, 60090, 90407, 132374, 189223, 264972, 364230, 492596, 656404, 863206, 1121449, 1441050, 1832997, 2310024, 2886128, 3577352, 4401210, 5377586, 6528059, 7876926, 9450419, 11277860
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(1) = 1, a(2) = 721, and if n > 2 then a(n) = (1/144)*(n^6 + 30*n^5
+ 463*n^4 + 3132*n^3 + 11506*n^2 + 10716*n - 1152
+ (n odd)(9*n^2 + 90*n + 261))
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CROSSREFS
| Cf. A159294 for analogous problem for strip-of-squares tile.
Sequence in context: A119452 A034179 A014440 * A154515 A053497 A139154
Adjacent sequences: A159292 A159293 A159294 * A159296 A159297 A159298
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KEYWORD
| nonn
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AUTHOR
| David Pasino (davepasino(AT)yahoo.com), Apr 09 2009
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EXTENSIONS
| Typo in formula corrected by David Pasino (davepasino(AT)yahoo.com), Apr 15 2009
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