#include <bits/stdc++.h>
#include <iostream>

using namespace std;
 
typedef long long ll;

typedef long double ld;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
#define i128 _int128

#define fi first
#define se second 
#define pb push_back

#define jintian return
#define shuawuti 0
#define endl '\n'

const ll INF=1e18;
const ll N=1e5+9,M=1e9+7;

int n,h[N],f;
ll ans,m;


void solve(){
    memset(h,0,sizeof(h));
    cin>>n;ans=1,f=0,m=0;
    for(int i=1;i<=n;++i){
        cin>>h[i];
        if(h[1]!=0 || h[i]==n)f=1;
        if(i>=2&&h[i]<h[i-1])f=1;
    }
    if(f)cout<<'0'<<endl;
    else{
        for(int i=2;i<=n;++i){
            if(h[i]>h[i-1]){
                ans*=2;
                m+=h[i]-h[i-1]-1;
            }
            if(h[i]==h[i-1]){
                if(m>=2){
                    ans*=m;
                    m--;
                }
                
            }
        }
        cout<<ans<<endl;
    }

}

int main(){
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    
    int _=1;
    cin>>_;
    
    while(_--)solve();

    jintian shuawuti;
}