## 1. Problem

The Tribonacci sequence Tn is defined as follows:

T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for n >= 0.

Given n, return the value of Tn.

Example 1:

```
Input: n = 4
Output: 4
Explanation:
T_3 = 0 + 1 + 1 = 2
T_4 = 1 + 1 + 2 = 4
```

Example 2:

```
Input: n = 25
Output: 1389537
```

Constraints:

- 0 <= n <= 37
- The answer is guaranteed to fit within a 32-bit integer, ie. answer <= 2^31 - 1.

## 2. Solution

I solved this problem like this.

```
class Solution:
def tribonacci(self, n: int) -> int:
tri = [0, 1, 1]
for i in range(35):
tri.append(sum(tri[-3:]))
return tri[n]
```