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A027910
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T(2n,n-2), T given by A027907.
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0
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1, 6, 36, 210, 1221, 7098, 41328, 241128, 1409895, 8260934, 48497064, 285219090, 1680166215, 9912297150, 58558256496, 346371955776, 2051126447742
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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COMMENTS
| a(n) is also the number of lattice paths from $(0,0)$ to \ $(2n+1,n-1)$ avoiding $% \uparrow ^{\geq 3}$ [From Shanzhen Gao (shanzhengao(AT)yahoo.com), Apr 20 2010]
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REFERENCES
| Shanzhen Gao, Pattern Avoidance in Paths and Walks, in preparation [From Shanzhen Gao (shanzhengao(AT)yahoo.com), Apr 20 2010]
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FORMULA
| a(n)=$\dsum\limits_{i=0}^{\lfloor (2n-1)/2\rfloor }\binom{2n+2}{n-1-i}\binom{n-1-i% }{i}$ [From Shanzhen Gao (shanzhengao(AT)yahoo.com), Apr 20 2010]
G.f.: -g^2*(g^2+g+1)/(3*g^2+g-1) where g = x times the g.f. of A143927. - Mark van Hoeij, Nov 16 2011
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CROSSREFS
| Sequence in context: A111989 A064238 A014336 * A075848 A096979 A123887
Adjacent sequences: A027907 A027908 A027909 * A027911 A027912 A027913
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KEYWORD
| nonn
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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