description: Let's call a sequence of integers x_1, x_2, ..., x_k MEX-correct if for all i (1 ≤ i ≤ k) |x_i - \operatorname{MEX}(x_1, x_2, ..., x_i)| ≤ 1 holds. Where \operatorname{MEX}(x_1, ..., x_k) is the minimum non-negative integer that doesn't belong to the set x_1, ..., x_k. For example, \operatorname{MEX}(1, 0, 1, 3) = 2 and \operatorname{MEX}(2, 1, 5) = 0.
  
  You are given an array a consisting of n non-negative integers. Calculate the number of non-empty MEX-correct subsequences of a given array. The number of subsequences can be very large, so print it modulo 998244353. 
  
  Note: a subsequence of an array a is a sequence [a_{i_1}, a_{i_2}, ..., a_{i_m}] meeting the constraints 1 ≤ i_1 < i_2 < ... < i_m ≤ n. If two different ways to choose the sequence of indices [i_1, i_2, ..., i_m] yield the same subsequence, the resulting subsequence should be counted twice (i. e. two subsequences are different if their sequences of indices [i_1, i_2, ..., i_m] are not the same).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^5) — the number of test cases.
  
  The first line of each test case contains a single integer n (1 ≤ n ≤ 5 ⋅ 10^5).
  
  The second line contains n integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ n).
  
  The sum of n over all test cases doesn't exceed 5 ⋅ 10^5.
  
  Output
  
  For each test case, print a single integer — the number of non-empty MEX-correct subsequences of a given array, taken modulo 998244353.
  
  Example
  
  Input
  
  
  4
  3
  0 2 1
  2
  1 0
  5
  0 0 0 0 0
  4
  0 1 2 3
  
  
  Output
  
  
  4
  2
  31
  7
  
  Note
  
  In the first example, the valid subsequences are [0], [1], [0,1] and [0,2].
  
  In the second example, the valid subsequences are [0] and [1].
  
  In the third example, any non-empty subsequence is valid. 
solution: import java.util.*;
  import java.util.Map.Entry;
  import java.io.*;
  import java.lang.*;
  
  public class Ccff {
  	
  	static class FastReader {
          BufferedReader br;
          StringTokenizer st;
   
          public FastReader()
          {
              br = new BufferedReader(
                  new InputStreamReader(System.in));
          }
   
          String next()
          {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  }
                  catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
   
          int nextInt() { return Integer.parseInt(next()); }
   
          long nextLong() { return Long.parseLong(next()); }
   
          double nextDouble()
          {
              return Double.parseDouble(next());
          }
   
          String nextLine()
          {
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
      }
  	
  	private static int mod = 998244353;
  	
  	static FastReader sc = new FastReader();
  
  	public static void main(String[] args) {
  		int t = sc.nextInt();
  		while(t-->0)
  			solve();
  
  	}
  	
  
  	private static void solve() {
  		int n = sc.nextInt();
  		int dp1[] = new int[n+2];
  		int dp2[] = new int[n+2];
  		dp1[0] = 1;
  		for(int i=0; i<n; i++) {
  			int x = sc.nextInt();
  			dp1[x + 1] = (dp1[x + 1] + dp1[x+1])%mod;
  			dp1[x + 1] = (dp1[x + 1] + dp1[x])%mod;
  		    if (x > 0) {
  		    	dp2[x - 1] = (dp2[x - 1] + dp2[x - 1])%mod;
  		    	dp2[x - 1] = (dp2[x - 1] + dp1[x - 1])%mod;
  		    }
  		    dp2[x + 1] = (dp2[x + 1] + dp2[x + 1])%mod;
  		}
  		int ans = 0;
  		for(int i=0; i<n+2; i++) {
  			ans = (ans + dp1[i])%mod;
  			ans = (ans + dp2[i])%mod;
  		}
  		ans = (ans+mod-1)%mod;
  		System.out.println(ans);
  	}
  
  }