A153372 Number of zig-zag paths from top to bottom of a rectangle of width 11 with 2n-1 rows whose color is that of the top right corner.

6, 20, 72, 264, 976, 3624, 13488, 50264, 187440, 699240, 2609008, 9735768, 36332016, 135588200, 506012592, 1888445784, 7047737776, 26302439784, 98161890288, 366344859224, 1367217022320, 5102522181480, 19042869606448

Offset

1,1

Links

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

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

Index entries for linear recurrences with constant coefficients, signature (6, -9, 2).

Formula

Empirical g.f. -2*x*(3-8*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+8*A001075(n))/3. - R. J. Mathar, Jun 16 2011

Crossrefs

A153368, A153369, A153370, A153371, A153373

Sequence in context: A146891 A235367 A189604 * A028402 A092760 A240043

Adjacent sequences: A153369 A153370 A153371 * A153373 A153374 A153375

Keyword

easy,nonn

Author

Joseph Myers, Dec 24 2008

Status

approved