1137. N-th Tribonacci Number

[mah-shamim]

Discussed in #219

^{Originally posted by mah-shamim August 2, 2024}
The Tribonacci sequence T_n is defined as follows:

T₀ = 0, T₁ = 1, T₂ = 1, and T_n+3 = T_n + Tn+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, i.e. answer <= 2^31 - 1.