#include<bits/stdc++.h>
#include <numeric>
#include <tuple>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>

using namespace std;
// using namespace __gnu_pbds;

// #define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>

#define all(v) v.begin(),v.end()
#define pb push_back
#define ll long long
ll mod =  998244353;


void solve() {
	int n;
	cin >> n;
	for (int i = 2; i < n + 1; i += 2)
	{
		cout << i << " " << i - 1 << " ";
	}
	cout << endl;

}


int main()
{


	int t;
	cin >> t;
	// t = 1;
	for (int i = 0; i < t; ++i)
	{
		solve();
	}
}