#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<set>
#include<stack>
#include<map>
#include<ctime>
#include<bitset>
#define LL long long
#define u64 unsigned long long
#define yy 137
#define INF 999999
#define maxn 100010
using namespace std;

int dp[maxn] ,a[maxn] ;
u64 sum1[maxn],sum2[maxn],pow1[maxn];
int main()
{
    int i,j,k,ans;
    int n,m,T,L,R,mid;
    u64 tt;
    pow1[0]=1;
    for( i = 1 ; i < maxn;i++)
        pow1[i]=pow1[i-1]*yy;
    cin >> T ;
    while(scanf("%d",&n)!= EOF)
    {
        for( i = 1 ; i <= n ;i++ )
        {
            scanf("%d",&a[i]) ;
            sum1[i]=sum1[i-1]+a[i]*pow1[i] ;
        }
        k = 1;
        sum2[n+1]=0;
        for( i = n ; i >= 1 ;i-- )
        {
            sum2[i]=sum2[i+1]+a[i]*pow1[k++] ;
        }
        ans=1;
        for( i = 1 ; i <= n ;i++)
        {
            if(a[i]>=a[i-1])dp[i]=dp[i-1]+1;
            else dp[i]=1;
            L=1;R=dp[i];
            while(L<=R)
            {
                mid=(L+R)>>1;
                j=n-(mid+i)+1;
                if(i-mid>=j){
                    tt=pow1[i-mid-j] ;
                    if(sum1[i]-sum1[i-mid]==tt*(sum2[i]-sum2[i+mid]))
                    {
                        L = mid+1;
                        ans=max(mid*2-1,ans) ;
                    }
                    else R =mid-1;
                }
                else{
                    tt=pow1[j-i+mid] ;
                    if((sum1[i]-sum1[i-mid])*tt==sum2[i]-sum2[i+mid])
                    {
                        L = mid+1;
                        ans=max(mid*2-1,ans) ;
                    }
                    else R =mid-1;
                }
            }
            L=1;R=dp[i];
           // cout << L << " " <<
            while(L<=R)
            {
                mid=(L+R)>>1;
                j=n-(mid+i+1)+1;/////
                if(i-mid>=j){
                    tt=pow1[i-mid-j] ;
                    if(sum1[i]-sum1[i-mid]==tt*(sum2[i+1]-sum2[i+1+mid]))
                    {
                        L = mid+1;
                        ans=max(mid*2,ans) ;
                    }
                    else R =mid-1;
                }
                else{
                    tt=pow1[j-i+mid] ;
                    if((sum1[i]-sum1[i-mid])*tt==sum2[i+1]-sum2[i+1+mid])
                    {
                        L = mid+1;
                        ans=max(mid*2,ans) ;
                    }
                    else R =mid-1;
                }
            }
        }
        cout << ans<<endl;
    }
    return  0;
}