1137. N-th Tribonacci Number

[F4NT0]

The Tribonacci sequence T_n is defined as follows:

T_0 = 0, T_1 = 1, T_2 = 1, and T_(n+3) = T_n + T_(n+1) + T_(n+2) for n >= 0.

Given n, return the value of T_n.

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.