A153370 Number of zig-zag paths from top to bottom of a rectangle of width 11 with n rows whose color is not that of the top right corner.

5, 10, 18, 36, 66, 132, 244, 488, 906, 1812, 3372, 6744, 12566, 25132, 46860, 93720, 174810, 349620, 652252, 1304504, 2433942, 4867884, 9083004, 18166008, 33897050, 67794100, 126503148, 253006296, 472111446, 944222892, 1761934444, 3523868888

Offset: 1

Author

Joseph Myers, Dec 24 2008

Keywords

• easy
• nonn

Links

• Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation
• Index entries for linear recurrences with constant coefficients, signature (0, 6, 0, -9, 0, 2).

Crossrefs

A153368, A153369, A153372. Bisections: A153371, A153373.

Formula

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