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A153337 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 4
1, 4, 24, 136, 720, 3624, 17584, 83024, 383904, 1746280, 7839216, 34812144, 153204064, 669108496, 2903267040, 12526343584, 53779871552, 229895033832, 978965187184, 4154438114480, 17575883030496, 74150192517808 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation

FORMULA

a(n) = (n)2^(2n-2) - 2(n-1)binomial(2n-2,n-1)

CROSSREFS

A102699, A153334, A153335, A153336, A153338

Sequence in context: A048180 A057391 A071079 * A122690 A183512 A204199

Adjacent sequences:  A153334 A153335 A153336 * A153338 A153339 A153340

KEYWORD

easy,nonn

AUTHOR

Joseph Myers, Dec 24 2008

STATUS

approved

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Last modified November 23 22:48 EST 2014. Contains 249866 sequences.