# Number of ways to paint 3 X N grid with 3 colors

![](https://1824821017-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M3rU5fVRA3qiBmK8Dbx%2F-M4hOMc9Ss4XgLOUqhQq%2F-M4hOefWVXzODNNeUySg%2FScreen%20Shot%202020-04-12%20at%2012.59.26%20AM.png?alt=media\&token=e35974ce-2258-458c-a65c-39e7c8dc8146)

看上面的解法就能推导出来，code部分其实简单。就是对于三种color来说，每一个column只有两种pattern

（1） 121

（2） 123

```python
class Solution:
    def numOfWays(self, n: int) -> int:
        a121 = 6
        a123 = 6
        mod = 10**9+7
        for _ in range(n-1):
            a121,a123 = a123*2 + 3* a121, a121*2 + 2*a123
            a121 = a121 % mod
            a123 = a123 % mod
        return (a121+a123) % mod
        
```