description: Monocarp has got an array a consisting of n integers. Let's denote k as the mathematic mean of these elements (note that it's possible that k is not an integer). 
  
  The mathematic mean of an array of n elements is the sum of elements divided by the number of these elements (i. e. sum divided by n).
  
  Monocarp wants to delete exactly two elements from a so that the mathematic mean of the remaining (n - 2) elements is still equal to k.
  
  Your task is to calculate the number of pairs of positions [i, j] (i < j) such that if the elements on these positions are deleted, the mathematic mean of (n - 2) remaining elements is equal to k (that is, it is equal to the mathematic mean of n elements of the original array a).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — the number of testcases.
  
  The first line of each testcase contains one integer n (3 ≤ n ≤ 2 ⋅ 10^5) — the number of elements in the array.
  
  The second line contains a sequence of integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ 10^{9}), where a_i is the i-th element of the array.
  
  The sum of n over all testcases doesn't exceed 2 ⋅ 10^5.
  
  Output
  
  Print one integer — the number of pairs of positions [i, j] (i < j) such that if the elements on these positions are deleted, the mathematic mean of (n - 2) remaining elements is equal to k (that is, it is equal to the mathematic mean of n elements of the original array a).
  
  Example
  
  Input
  
  
  4
  4
  8 8 8 8
  3
  50 20 10
  5
  1 4 7 3 5
  7
  1 2 3 4 5 6 7
  
  
  Output
  
  
  6
  0
  2
  3
  
  Note
  
  In the first example, any pair of elements can be removed since all of them are equal.
  
  In the second example, there is no way to delete two elements so the mathematic mean doesn't change.
  
  In the third example, it is possible to delete the elements on positions 1 and 3, or the elements on positions 4 and 5.
solution: 
  import java.util.*;
  import java.io.*;
  import java.math.*;
  
  
  
  public class Main {
  	  static class Reader{
  		  
  			BufferedReader br;
  			StringTokenizer st;
  			public Reader() {
  				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; 
  		    } 
  		}
  	 
  	  static long mod = (long)(1e9 + 7);
  	 
  	static void sort(long[] arr ) {
  		 ArrayList<Long> al = new ArrayList<>();
  		 for(long e:arr) al.add(e);
  		 Collections.sort(al);
  		 for(int i = 0 ; i<al.size(); i++) arr[i] = al.get(i);
  	 }
  	static void sort(int[] arr ) {
  		 ArrayList<Integer> al = new ArrayList<>();
  		 for(int e:arr) al.add(e);
  		 Collections.sort(al);
  		 for(int i = 0 ; i<al.size(); i++) arr[i] = al.get(i);
  	 }
  	static void sort(char[] arr) {
  		ArrayList<Character> al = new ArrayList<Character>();
  		for(char cc:arr) al.add(cc);
  		Collections.sort(al);
  		for(int i = 0 ;i<arr.length ;i++) arr[i] = al.get(i);
  	}
  	static void rvrs(int[] arr) {
  		int i =0 , j = arr.length-1;
  		while(i>=j) {
  			int temp = arr[i];
  			arr[i] = arr[j];
  			arr[j] = temp;
  			i++;
  			j--;
  		}
  	}
  	static long[] rvrs(long[] arr) {
  		int i =0 , j = arr.length-1;
  		int n = arr.length;
  		long[] ans = new long[n];
  		for( i =0 ; i<n ; i++)
  			ans[i] = arr[j--];
  		return ans;
  	}
  
  	static long mod_mul(long a , long b ,long mod) {
  		return ((a%mod)*(b%mod))%mod;
  	}
  	 static long gcd(long a, long b)
  	  {      
  	     if (b == 0)
  	        return a;
  	     return gcd(b, a % b); 
  	  }
  	 static boolean[] prime(int num) {
  			boolean[] bool = new boolean[num];
  		     
  		      for (int i = 0; i< bool.length; i++) {
  		         bool[i] = true;
  		      }
  		      for (int i = 2; i< Math.sqrt(num); i++) {
  		         if(bool[i] == true) {
  		            for(int j = (i*i); j<num; j = j+i) {
  		               bool[j] = false;
  		            }
  		         }
  		      }
  		      if(num >= 0) {
  		    	  bool[0] = false;
  		    	  bool[1] = false;
  		      }
  		      
  		      return bool;
  		}
  
  	 static long modInverse(long a, long m)
  	    {
  	        long g = gcd(a, m);
  	       
  	          return   power(a, m - 2, m);
  	        
  	    }
  	   
  	 static long power(long x, long y, long m){
  	        if (y == 0) return 1; long p = power(x, y / 2, m) % m; p = (int)((p * (long)p) % m);
  	        if (y % 2 == 0) return p; else return (int)((x * (long)p) % m); }
  	   
       static class Combinations{
  	    	 private long[] z;
  	    	 private long[] z1;
  	    	 private long[] z2;
  	    	 long MOD;
  	    	  public Combinations(long N , long mod) {
  	    		  MOD  = mod;
  				z = new long[(int)N+1];
  				z1 = new long[(int)N+1];
  				z[0] = 1;
  				for(int i =1 ; i<=N ; i++) z[i] = (z[i-1]*i)%MOD;
  			     z2 = new long[(int)N+1];
  				z2[0] = z2[1] = 1;
  			    for (int i = 2; i <= N; i++)
  			        z2[i] = z2[(int)(MOD % i)] * (MOD - MOD / i) % MOD;
  			    
  			    
  			    z1[0] = z1[1] = 1;
  			    
  			    for (int i = 2; i <= N; i++)
  			        z1[i] = (z2[i] * z1[i - 1]) % MOD;
  			}
  	    	  long fac(long n) {
  	    		  return z[(int)n];
  	    	  }
  	    	  long invrsNum(long n) {
  	    		  return z2[(int)n];
  	    	  }
  	    	  long invrsFac(long n) {
  	    		  return invrsFac((int)n);
  	    	  }
  	    	  long ncr(long N, long R)
  	    	  {		if(R<0 || R>N ) return 0;
  	    		    long ans = ((z[(int)N] * z1[(int)R])
  	    		              % MOD * z1[(int)(N - R)])
  	    		             % MOD;
  	    		    return ans;
  	    		}
  	      }
       static class DisjointUnionSets {
           private int[] parent;  // parent[i] = parent of i
           private byte[] rank;   // rank[i] = rank of subtree rooted at i (never more than 31)
           private int count;     // number of components
           private int[] size;
           public DisjointUnionSets(int n) {
               if (n < 0) throw new IllegalArgumentException();
               count = n;
               parent = new int[n];
               rank = new byte[n];
               size = new int[n];
               for (int i = 0; i < n; i++) {
                   parent[i] = i;
                   rank[i] = 0;
                   size[i] = 1;
               }
           }
    
           public int find(int p) {
               while (p != parent[p]) {
                   parent[p] = parent[parent[p]];    // path compression by halving
                   p = parent[p];
               }
               return p;
           }
    
           public int count() {
               return count;
           }
    
           public boolean connected(int p, int q) {
               return find(p) == find(q);
           }
    
           public void union(int p, int q) {
               int rootP = find(p);
               int rootQ = find(q);
               if (rootP == rootQ) return;
    
               // make root of smaller rank point to root of larger rank
               if (rank[rootP] < rank[rootQ]) {
                   parent[rootP] = rootQ;
                   size[rootQ] = size[rootQ] + size[rootP];
               }
               else if (rank[rootP] > rank[rootQ]) {
                   parent[rootQ] = rootP;
                   size[rootP] = size[rootP] + size[rootQ];
               }
               else {
                   parent[rootQ] = rootP;
                   size[rootP] = size[rootP] + size[rootQ];
                   rank[rootP]++;
               }
               count--;
           }
       }
  	      static int[] KMP(String str) {
  	    	  int n = str.length();
  	    	  int[] kmp = new int[n];
  	    	  for(int i = 1 ; i<n ; i++) {
  	    		  int j = kmp[i-1];
  	    		  while(j>0 && str.charAt(i) != str.charAt(j)) {
  	    			  j = kmp[j-1];
  	    		  }
  	    		  if(str.charAt(i) == str.charAt(j)) j++;
  	    		  kmp[i] = j;
  	    	  }
  	    	  
  	    	  return kmp;
  	      }
  	      
  	      
  /************************************************ Query **************************************************************************************/	  
  	 
  /***************************************** 		Sparse Table	********************************************************/
  	      static class SparseTable{
  	    		
  	    		private long[][] st;
  	    		
  	    		SparseTable(long[] arr){
  	    			int n = arr.length;
  	    			st = new long[n][25];
  	    			log = new int[n+2];
  	    			build_log(n+1);
  	    			build(arr);
  	    		}
  	    		
  	    		private void build(long[] arr) {
  	    			int n = arr.length;
  	    			
  	    			for(int i = n-1 ; i>=0 ; i--) {
  	    				for(int j = 0 ; j<25 ; j++) {
  	    					int r = i + (1<<j)-1;
  	    					if(r>=n) break;
  	    					if(j == 0 ) st[i][j] = arr[i];
  	    					else st[i][j] = Math.min(st[i][j-1] , st[ i + ( 1 << (j-1) ) ][ j-1 ] );
  	    				}
  	    			}
  	    		}
  	    		public long gcd(long a  ,long b) {
  	    			if(a == 0) return b;
  	    			return gcd(b%a , a);
  	    		}
  	    		public long query(int l ,int r) {
  	    			
  	    			int w = r-l+1;
  	    			int power = log[w];
  	    			return Math.min(st[l][power],st[r - (1<<power) + 1][power]);
  	    		}
  	    		private int[] log;
  	    		void build_log(int n) {
  	    			log[1] = 0;
  	    			for(int i = 2 ; i<=n ; i++) {
  	    				log[i] = 1 + log[i/2];
  	    			}
  	    		}
  	    	}
  	      
  	      
  /********************************************************	Segement Tree	*****************************************************/
  /**
  	 	 static class SegmentTree{
  			 long[] tree;
  			 long[] arr;
  			 int n;
  			 SegmentTree(long[] arr){
  				 this.n = arr.length;
  				 tree = new long[4*n+1];
  				 this.arr = arr;
  				 buildTree(0, n-1, 1);
  			 }
  			 
  			 
  			  void buildTree(int s ,int e  ,int index ) {
  					if(s == e) {
  						tree[index] = arr[s];
  						return;
  					}
  				
  					int mid = (s+e)/2;
  					
  					buildTree( s,  mid, 2*index);
  					buildTree( mid+1, e, 2*index+1);
  					
  					tree[index] = Math.min(tree[2*index] , tree[2*index+1]);
  				}
  			  
  			 long query(int si ,int ei) {
  				 return query(0 ,n-1 , si ,ei , 1   );
  			 }
  			 private long query( int ss ,int se ,int qs , int qe,int index) {
  					
  					if(ss>=qs && se<=qe) return tree[index];
  					
  					if(qe<ss || se<qs) return (long)(1e17);
  					
  					int mid = (ss + se)/2;
  					long left = query( ss , mid , qs ,qe , 2*index);
  					long right= query(mid + 1 , se , qs ,qe , 2*index+1);
  					return Math.min(left, right);
  				}
  			 public void update(int index , int val) {
  				 arr[index] = val;
  				 for(long e:arr) System.out.print(e+" ");
  				 update(index , 0 , n-1 , 1);
  			 }
  			 private void update(int id ,int si , int ei , int index) {
  				 if(id < si || id>ei) return;
  				 if(si == ei ) { 
  					 tree[index] = arr[id];
  					 return;
  				 }
  				 if(si > ei) return;
  				 int mid = (ei + si)/2;
  					
  					update( id,  si, mid , 2*index);
  					update( id , mid+1, ei , 2*index+1);
  					
  					tree[index] = Math.min(tree[2*index] ,tree[2*index+1]);
  			 }
  			  
  		 }
  		 */
  
  /* ***************************************************************************************************************************************************/	 
  	 
  	      static Reader sc = new Reader();
  	 static StringBuilder sb = new StringBuilder();
  	 public static void main(String args[])  {
  	
  		 int tc = 1;
  		  tc = sc.nextInt();
  		 
  		  for(int i = 1 ; i<=tc ; i++) {
  
  //			 sb.append("Case #" + i + ": "  );	// During KickStart && HackerCup
  			 TEST_CASE();
  			 
  		 }
  		 System.out.println(sb);
  
  	 }
  
  	static void TEST_CASE() {
  		int n = sc.nextInt();
  		long[] arr = new long[n];
  		for(int i = 0 ; i<n ; i++)
  			arr[i] = sc.nextLong();
  		long sum = 0;
  		for(long e:arr) sum += e;
  		sort(arr);
  		sum *= (n-2);
  		long[] na = new long[n];
  		for(int i = 0 ; i<n ; i++) {
  			na[i] = arr[i]*n;
  		}
  		long nsum = 0;
  		for(long e:na) nsum += e;
  		Map<Long , Long> map = new HashMap<>();
  		for(int i = 0 ; i< n ; i++) {
  			if(!map.containsKey(na[i])) map.put(na[i], 1l);
  			else map.put(na[i], map.get(na[i])+1l);
  		}
  		int i = 0 ;
  		long ans = 0;
  		while(i<n ) {
  			long pe = na[i];
  			while(i<n && pe == na[i]) i++;
  			long e2 = nsum - sum - pe;
  			if(pe<=e2) {
  				if(pe == e2) {
  					long count = map.get(pe);
  					count *= (count-1);
  					count /= 2;
  					ans += count;
  				}else {
  					if(map.containsKey(e2)) {
  						ans += map.get(e2)*map.get(pe);
  					}
  				}
  			}
  		}
  		sb.append(ans+"\n");
  	}
  }
  
  /*******************************************************************************************************************************************************/
  
  /**
  
   */
  
  
  
  
  
  
  