T = int(input())
for _ in range(T):
    N = int(input())
    ans = list()
    if N%2==0:
        for i in range(0,N,2):
            ans.append(i+2)
            ans.append(i+1)
    else:
        for i in range(0,N-3,2):
            ans.append(i+2)
            ans.append(i+1)
        ans.append(N-1)
        ans.append(N)
        ans.append(N-2)
    print(*ans)