description: British mathematician John Littlewood once said about Indian mathematician Srinivasa Ramanujan that "every positive integer was one of his personal friends."
  
  It turns out that positive integers can also be friends with each other! You are given an array a of distinct positive integers. 
  
  Define a subarray a_i, a_{i+1}, …, a_j to be a friend group if and only if there exists an integer m ≥ 2 such that a_i mod m = a_{i+1} mod m = … = a_j mod m, where x mod y denotes the remainder when x is divided by y.
  
  Your friend Gregor wants to know the size of the largest friend group in a.
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 2⋅ 10^4). 
  
  Each test case begins with a line containing the integer n (1 ≤ n ≤ 2 ⋅ 10^5), the size of the array a.
  
  The next line contains n positive integers a_1, a_2, …, a_n (1 ≤ a_i ≤ {10}^{18}), representing the contents of the array a. It is guaranteed that all the numbers in a are distinct.
  
  It is guaranteed that the sum of n over all test cases is less than 2⋅ 10^5.
  
  Output
  
  Your output should consist of t lines. Each line should consist of a single integer, the size of the largest friend group in a.
  
  Example
  
  Input
  
  
  4
  5
  1 5 2 4 6
  4
  8 2 5 10
  2
  1000 2000
  8
  465 55 3 54 234 12 45 78
  
  
  Output
  
  
  3
  3
  2
  6
  
  Note
  
  In the first test case, the array is [1,5,2,4,6]. The largest friend group is [2,4,6], since all those numbers are congruent to 0 modulo 2, so m=2.
  
  In the second test case, the array is [8,2,5,10]. The largest friend group is [8,2,5], since all those numbers are congruent to 2 modulo 3, so m=3.
  
  In the third case, the largest friend group is [1000,2000]. There are clearly many possible values of m that work.
solution: /*
      Author : Akshat Jindal
      from NIT Jalandhar , Punjab , India
      JAI MATA DI
   */
  import java.util.*;
  import java.io.*;
  import java.math.*;
  import java.sql.Array;
  
  
  
  public class Main {
  	  static class FR{
  		  
  			BufferedReader br;
  			StringTokenizer st;
  			public FR() {
  				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 int UB(long[] arr , long find , int l , int r) {
  		while(l<=r) {
  			int m = (l+r)/2;
  			if(arr[m]<find) l = m+1;
  			else r = m-1;
  		}
  		return l;
  	}
  	static int LB(long[] arr , long find,int l ,int r ) {
  		while(l<=r) {
  			int m = (l+r)/2;
  			if(arr[m] > find) r = m-1;
  			else l = m+1;
  		}
  		return r;
  	}
  	static int UB(int[] arr , long find , int l , int r) {
  		while(l<=r) {
  			int m = (l+r)/2;
  			if(arr[m]<find) l = m+1;
  			else r = m-1;
  		}
  		return l;
  	}
  	static int LB(int[] arr , long find,int l ,int r ) {
  		while(l<=r) {
  			int m = (l+r)/2;
  			if(arr[m] > find) r = m-1;
  			else l = m+1;
  		}
  		return r;
  	}
  	 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 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 long[][] ncr(int n, int k)
  	    {
  	        long C[][] = new long[n + 1][k + 1];
  	        int i, j;
  	 
  	        // Calculate  value of Binomial
  	        // Coefficient in bottom up manner
  	        for (i = 0; i <= n; i++) {
  	            for (j = 0; j <= Math.min(i, k); j++) {
  	                // Base Cases
  	                if (j == 0 || j == i)
  	                    C[i][j] = 1;
  	 
  	                // Calculate value using
  	                // previously stored values
  	                else
  	                    C[i][j] = (C[i - 1][j - 1] + C[i - 1][j])%mod;
  	            }
  	        }
  	 
  	        return C;
  	    }
  	 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 DisjointUnionSets {
  			    int[] rank, parent;
  			    int n;
  			  
  			    public DisjointUnionSets(int n)
  			    {
  			        rank = new int[n];
  			        parent = new int[n];
  			        this.n = n;
  			        makeSet();
  			    }
  			  
  			    void makeSet()
  			    {
  			        for (int i = 0; i < n; i++) {
  			          
  			            parent[i] = i;
  			        }
  			    }
  			  
  			    int find(int x)
  			    {
  			        if (parent[x] != x) {
  			        
  			            parent[x] = find(parent[x]);
  			  
  			        }
  			  
  			        return parent[x];
  			    }
  			  
  			    void union(int x, int y)
  			    {
  			        int xRoot = find(x), yRoot = find(y);
  			  
  			        if (xRoot == yRoot)
  			            return;
  			  
  			        if (rank[xRoot] < rank[yRoot])
  			  
  			            parent[xRoot] = yRoot;
  			  
  			        else if (rank[yRoot] < rank[xRoot])
  			  
  			            parent[yRoot] = xRoot;
  			  
  			        else
  			        {
  			            parent[yRoot] = xRoot;
  			  
  			            rank[xRoot] = rank[xRoot] + 1;
  			        }
  			    }
  			}
  //	  	static int query(int[] tree , int ss ,int se ,int qs , int qe,int index) {
  //			
  //			if(ss>=qs && se<=qe) return tree[index];
  //			
  //			if(qe<ss || se<qs) return Integer.MAX_VALUE;
  //			
  //			int mid = (ss + se)/2;
  //			int left = query(tree , ss , mid , qs ,qe , 2*index);
  //			int right= query(tree ,mid + 1 , se , qs ,qe , 2*index+1);
  //			return Math.min(left, right);
  //		}
  //		static void buildTree(int[] a ,int s ,int e ,int[] tree ,int index ) {
  //			if(s == e) {
  //				tree[index] = a[s];
  //				return;
  //			}
  //		
  //			int mid = (s+e)/2;
  //			
  //			buildTree(a, s,  mid, tree, 2*index);
  //			buildTree(a, mid+1, e, tree, 2*index+1);
  //			
  //			tree[index] = tree[2*index] + tree[2*index+1];
  //		}
  /* ***************************************************************************************************************************************************/	 
  	 
  	      static FR sc = new FR();
  	 static StringBuilder sb = new StringBuilder();
  	 public static void main(String args[]) {
  		
  		 int tc = 1;
  		  tc = sc.nextInt();
  
  		 while(tc-->0) {
  			 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[] sub = new long[n-1];
  		 
  		 for(int i =0 ; i<n-1 ; i++)
  			 sub[i] = Math.abs(arr[i] - arr[i+1]);
  		 
  		 SparseTable st = new SparseTable(sub);
  		 long ans = 0;
  		 for(int i = 0 ; i<sub.length ;i++) {
  			 int l = i , r = sub.length-1;
  			 while(l<=r) {
  				 int m = (l+r)/2;
  				 if(st.query(i, m) <=1) r = m-1;
  				 else l = m+1;
  			 }
  			 ans = Math.max(ans, r - i+1);
  		 }
  		 sb.append((ans+1)+"\n");
  	 }
  	 
  
  	 
  
  }
  
  
  
  /*******************************************************************************************************************************************************/
  
    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] = gcd(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 gcd(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];
  		}
  	}
  }
  
  
  
  
  
  
  