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A153371 Number of zig-zag paths from top to bottom of a rectangle of width 11 with 2n rows whose color is that of the top right corner. 4
10, 36, 132, 488, 1812, 6744, 25132, 93720, 349620, 1304504, 4867884, 18166008, 67794100, 253006296, 944222892, 3523868888, 13151219892, 49080945144, 183172429612, 683608511160, 2551261090740, 9521434803224, 35534476025004 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..23.

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

FORMULA

Empirical: G.f. -2*x*(5-12*x+3*x^2) / ( (2*x-1)*(x^2-4*x+1) ) with a(n)= +6*a(n-1) -9*a(n-2) +2*a(n-3) and a(n) = (2^n+4*A001075(n+1))/3. - R. J. Mathar, Jun 16 2011

CROSSREFS

A153368, A153369, A153370, A153372, A153373

Sequence in context: A118415 A051959 A117327 * A248463 A169880 A282554

Adjacent sequences:  A153368 A153369 A153370 * A153372 A153373 A153374

KEYWORD

easy,nonn

AUTHOR

Joseph Myers, Dec 24 2008

STATUS

approved

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Last modified January 20 08:18 EST 2020. Contains 331081 sequences. (Running on oeis4.)