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A153363
Number of zig-zag paths from top to bottom of a rectangle of width 9 with n rows whose color is that of the top right corner
5
5, 8, 16, 28, 56, 100, 200, 360, 720, 1300, 2600, 4700, 9400, 17000, 34000, 61500, 123000, 222500, 445000, 805000, 1610000, 2912500, 5825000, 10537500, 21075000, 38125000, 76250000, 137937500, 275875000, 499062500, 998125000, 1805625000
OFFSET
1,1
FORMULA
Empirical g.f.: x*(5+8*x-9*x^2-12*x^3+x^4)/(1-5*x^2+5*x^4). [Colin Barker, Sep 02 2012]
KEYWORD
easy,nonn
AUTHOR
Joseph Myers, Dec 24 2008
STATUS
approved