#include <bits/stdc++.h>
 
using namespace std;
 
#define int long long
#define nn "\n"
#define pi pair<int, int>
#define fi first
#define se second
#define lb lower_bound
#define ub upper_bound
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define eb emplace_back
 
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int t;
    cin >> t;
 
    while (t--) {
        int n;
    cin >> n;
    vector<long long> b(n);
    for (int i = 0; i < n; ++i) {
        long long a;
        cin >> a;
        b[i] = a - (i + 1);
    }
    sort(b.begin(), b.end());
    b.erase(unique(b.begin(), b.end()), b.end());
 
    int max_len = 1;
    int cur_len = 1;
    for (size_t i = 1; i < b.size(); ++i) {
        if (b[i] == b[i - 1] + 1) {
            cur_len++;
        } else {
            cur_len = 1;
        }
        max_len = max(max_len, cur_len);
    }
    cout << max_len << "\n";
    }
 
    return 0;
}

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OAo1CjUgNSA1IDkgOAo2CjYgNiA2IDYgNiA2CjUKNSA2IDcgOCA5CjUKOSA3IDEyIDEwIDEyCjQKNCA3IDUgOAo3CjE0IDkgMTQgMTIgOCAxMSAxMgo1CjEwMDAwMDAwMDAgMTAwMDAwMDAwMCAxMDAwMDAwMDAwIDEwMDAwMDAwMDAgMTAwMDAwMDAwMAo4CjggOCAxMiA4IDE0IDEwIDE1IDEzCg==

8
5
5 5 5 9 8
6
6 6 6 6 6 6
5
5 6 7 8 9
5
9 7 12 10 12
4
4 7 5 8
7
14 9 14 12 8 11 12
5
1000000000 1000000000 1000000000 1000000000 1000000000
8
8 8 12 8 14 10 15 13