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A153334
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Number of zig-zag paths from top to bottom of an n by n square whose color is that of the top right corner
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4
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1, 1, 4, 8, 24, 52, 136, 296, 720, 1556, 3624, 7768, 17584, 37416, 83024, 175568, 383904, 807604, 1746280, 3657464, 7839216, 16357496, 34812144, 72407728, 153204064, 317777032, 669108496, 1384524656, 2903267040, 5994736336
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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LINKS
| Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation
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FORMULA
| a(n) = (n+1)2^(n-2) - 2(n-1)binomial(n-2,(n-2)/2) for n even, a(n) = (n+1)2^(n-2) - (n-1)binomial(n-1,(n-1)/2) for n odd
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CROSSREFS
| A102699, A153335, A153336, A153337, A153338
Sequence in context: A006640 A180002 A115641 * A159612 A099176 A190156
Adjacent sequences: A153331 A153332 A153333 * A153335 A153336 A153337
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KEYWORD
| easy,nonn
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AUTHOR
| Joseph Myers (jsm(AT)polyomino.org.uk), Dec 24 2008
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