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Tribonacci Sequence
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Matrices (2D Arrays)
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# Tribonacci Sequence

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## Problem Statement

#### You are given an integer ‘N’. Your task is to find out the ‘N’th Tribonacci Number. ‘N’th number in the Tribonacci sequence is defined as Tn = T n - 1 + Tn - 2 + Tn - 3. Where T0 = 0, T1 = 1, T2= 1. Return the answer in mod of 109 + 7.

##### For Example :
``````You are given ‘N’ = 5, Here we know 0th, 1st and 2nd Tribonacci numbers are 0, 1 and 1 respectively. Therefore we can calculate the 3rd number as 0 + 1 + 1 = 2 and 4th number as 1 + 1 + 2 = 4 and 5th number as 1 + 2 + 4 = 7. Hence the answer is 7.
``````
``````Can you solve it in logarithmic time?
``````
Detailed explanation ( Input/output format, Notes, Constraints, Images ) ##### Sample Input 1 :
``````2
5
2
``````
##### Sample Output 1 :
``````7
1
``````
##### Explanation for Sample Input 1:
``````For the first test case, ‘N’ = 5, Here we know 0th, 1st and 2nd Tribonacci numbers are 0, 1 and 1 respectively. Therefore we can calculate the 3rd number as 0 + 1 + 1 = 2 and 4th number as 1 + 1 + 2 = 4 and 5th number as 1 + 2 + 4 = 7. Hence the answer is 7.

For the second test case, ‘N’ = 2, Here, the second number in the Tribonacci sequence is already defined as 1. Hence the answer is 1.
``````
##### Sample Input 2 :
``````2
0
9
``````
##### Sample Output 2 :
``````0
81
``````  Auto Console