Suppose we can only use 5 kinds of tiles to cover a $1\times n$ board:

(1) $1\times 1$ size with red color,

(2) $1\times 1$ size with blue color,

(3) $1\times 2$ size with black color,

(4) $1\times 2$ size with green color,

(5) $1\times 2$ size with white color.

Let W(n) be the number of ways to tile the $1\times n$ board, $n=1,2,\dots $

For example, $W(1)=2$, $W(2)=7$.

What is the W(n) equation?

(1) $1\times 1$ size with red color,

(2) $1\times 1$ size with blue color,

(3) $1\times 2$ size with black color,

(4) $1\times 2$ size with green color,

(5) $1\times 2$ size with white color.

Let W(n) be the number of ways to tile the $1\times n$ board, $n=1,2,\dots $

For example, $W(1)=2$, $W(2)=7$.

What is the W(n) equation?