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A153337
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Number of zig-zag paths from top to bottom of a 2n-1 by 2n-1 square whose color is that of the top right corner
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4
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1, 4, 24, 136, 720, 3624, 17584, 83024, 383904, 1746280, 7839216, 34812144, 153204064, 669108496, 2903267040, 12526343584, 53779871552, 229895033832, 978965187184, 4154438114480, 17575883030496, 74150192517808
(list;
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listen;
history;
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internal format)
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..22.
Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation
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FORMULA
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a(n) = (n)2^(2n-2) - 2(n-1)binomial(2n-2,n-1)
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CROSSREFS
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A102699, A153334, A153335, A153336, A153338
Sequence in context: A048180 A057391 A071079 * A122690 A183512 A204199
Adjacent sequences: A153334 A153335 A153336 * A153338 A153339 A153340
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KEYWORD
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easy,nonn
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AUTHOR
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Joseph Myers, Dec 24 2008
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STATUS
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approved
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