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A059714
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Number of stacked directed animals on the triangular lattice.
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0
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1, 3, 11, 44, 184, 789, 3435, 15100, 66806, 296870, 1323318, 5911972, 26455294, 118528793, 531540891, 2385375732, 10710619014, 48112492938, 216195753066, 971744791032, 4368674392104, 19643610378738, 88339070102046
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Closely related to directed animals. A square lattice version exists.
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REFERENCES
| M. Bousquet-Melou and A. Rechnitzer, Lattice animals and heaps of dimers, Discrete Math. 258 (2002), no. 1-3, 235-274.
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LINKS
| M. Bousquet-Melou and A. Rechnitzer, Lattice animals and heaps of dimers
M. Bousquet-Melou and S. Butler, Forest-like permutations
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FORMULA
| G.f.: ((1-3x)(1-4x)-(1-5x)sqrt(1-4x))/(2x(2-9x))
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MAPLE
| gf := ((1-3*x)*(1-4*x)-(1-5*x)*sqrt(1-4*x))/(2*x*(2-9*x)): s := series(gf, x, 50): for i from 1 to 100 do printf(`%d, `, coeff(s, x, i)) od:
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CROSSREFS
| Cf. A005773.
Sequence in context: A200613 A149073 A167011 * A059715 A026748 A113174
Adjacent sequences: A059711 A059712 A059713 * A059715 A059716 A059717
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KEYWORD
| nonn
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AUTHOR
| Mireille Bousquet-Melou (bousquet(AT)labri.u-bordeaux.fr), Feb 08 2001
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu), Feb 09 2001
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