#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;
}