|
| |
|
|
A060521
|
|
Number of 3 X n grids of black and white cells, no 3 of same color vertically or horizontally contiguous.
|
|
1
| |
|
|
6, 36, 102, 378, 1260, 4374, 14946, 51384, 176238, 605022, 2076288, 7126302, 24457806, 83942100, 288096942, 988778082, 3393583068, 11647114446, 39974047290, 137194888728, 470866430838, 1616060190870, 5546478488640
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| The conjectured recursion is correct: For each n count the solutions separately where the last two rows differ in 0, 1, 2, or 3 places; a linear recursion is then readily found. The corresponding matrix has characteristic polynomial x^4 - 2 x^3 - 5 x^2 + 1, matching the recursion recursion a(n+4) = 2a(n+3) + 5a(n+2) - a(n). [From Hagen von Eitzen (math(AT)von-eitzen.de), Oct 21 2009]
|
|
|
FORMULA
| Almost surely satisfies a(n+4) = 2a(n+3) + 5a(n+2) - a(n).
|
|
|
CROSSREFS
| Sequence in context: A207070 A207118 A207249 * A036141 A199243 A172137
Adjacent sequences: A060518 A060519 A060520 * A060522 A060523 A060524
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Tom Womack (tom(AT)womack.net)
|
|
|
EXTENSIONS
| More terms from Hagen von Eitzen (math(AT)von-eitzen.de), Oct 21 2009
|
| |
|
|
