#include <bits/stdc++.h>
using namespace std;
#define SC scanf
#define PF printf
#define ull unsigned long long
#define ld long double
#define F first
#define S second
#define pb push_back
#define sort_a(a) sort(a.begin(),a.end());
#define sort_d(a) sort(a.rbegin(),a.rend());
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)
#define rev(s) reverse(s.begin(),s.end())
#define P(ok) cout << (ok ? "YES\n": "NO\n")
#define __Heart__ ios_base :: sync_with_stdio(false); cin.tie(NULL);
#define ll long long
typedef pair< ll , ll> PII;
void solve()
{
int n ; cin >> n ; vector < int > Ans(n) ;
int cur = 2 ;
if(n % 2 == 0){
for(int i = 0 ; i < n ; i += 2){
Ans[i] = cur ;
Ans[i + 1] = cur - 1 ;
cur += 2 ;
}
}
else {
Ans[0] = 2 ;
Ans[1] = 3 ;
Ans[2] = 1 ;
cur = 5 ;
for(int i = 3 ; i < n ; i += 2) {
Ans[i] = cur ;
Ans[i + 1] = cur - 1 ;
cur += 2 ;
}
}
for(auto it : Ans) cout << it << " " ; cout << endl ;
}
int main()
{
__Heart__
int t ; cin >> t ; while(t--) solve() ;
}