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A153365
Number of zig-zag paths from top to bottom of a rectangle of width 9 with 2n rows whose color is that of the top right corner.
5
8, 28, 100, 360, 1300, 4700, 17000, 61500, 222500, 805000, 2912500, 10537500, 38125000, 137937500, 499062500, 1805625000, 6532812500, 23635937500, 85515625000, 309398437500, 1119414062500, 4050078125000, 14653320312500
OFFSET
1,1
FORMULA
Empirical G.f.: x*(8-12*x)/(1-5*x+5*x^2). - Colin Barker, Jan 04 2012
KEYWORD
nonn,easy
AUTHOR
Joseph Myers, Dec 24 2008
STATUS
approved