[백준]9095 - 1, 2, 3 더하기(설명X)

#include <iostream>
using namespace std;
 
int main() {
    int T, n;
    cin >> T;
 
    int arr[11][3] = { 0, };
    arr[1][0] = 1;
    for (int i = 1; i < 10; i++) {
        arr[i + 1][0] = arr[i][0] + arr[i][1] + arr[i][2];
        arr[i + 1][1] = arr[i][0];
        arr[i + 1][2] = arr[i][1];
    }
 
    for (int i = 0; i < T; i++) {
        cin >> n;
        cout << arr[n][0] + arr[n][1] + arr[n][2] << endl;
    }
}