#include <iostream>
#include <vector>
 
using namespace std;
 
const int MOD = 998244353;
 
int countWays(vector<int>& p) {
    int n = p.size();
    vector<int> dp(n + 1, 0);
    dp[0] = 1;
 
    for (int i = 1; i <= n; ++i) {
        dp[i] = (2 * dp[i - 1]) % MOD;
    }
 
    vector<bool> visited(n + 1, false);
    int ans = 1;
 
    for (int i = 0; i < n; ++i) {
        if (!visited[p[i]]) {
            visited[p[i]] = true;
        } else {
            ans = (ans * dp[i]) % MOD;
        }
    }
 
    return ans;
}
 
int main() {
    int t;
    cin >> t;
 
    while (t--) {
        int n;
        cin >> n;
 
        vector<int> p(n);
        for (int i = 0; i < n; ++i) {
            cin >> p[i];
        }
 
        int result = countWays(p);
        cout << result << endl;
    }
 
    return 0;
}