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Search: id:A135389
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| A135389 |
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Number of walks from origin to (1,1) in a square lattice. |
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+0
1
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| 2, 24, 300, 3920, 52920, 731808, 10306296, 147232800, 2127513960, 31031617760, 456164781072, 6749962774464, 100445874620000, 1502052155856000, 22557604697766000, 340044833169460800, 5143178101688094600
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) is the number of walks of length 2n+2 in an infinite square lattice that begin at the origin and end at (1,1) using steps (1,0), (-1,0), (0,1), (0,-1).
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LINKS
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S. Hollos and R. Hollos, Lattice Paths and Walks.
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FORMULA
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a(n) = binomial(2n+2,n) * binomial(2n+2,n+1)
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CROSSREFS
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Cf. A002894, A060150.
Sequence in context: A002006 A065101 A052739 this_sequence A065513 A119491 A001864
Adjacent sequences: A135386 A135387 A135388 this_sequence A135390 A135391 A135392
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KEYWORD
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easy,nonn
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AUTHOR
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Stefan Hollos (stefan(AT)exstrom.com), Dec 11 2007
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