#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() ;
}