def construct_doubled_sequence(N):
    sequence = [-1] * (2 * N)
    for i in range(1, N + 1):
        if sequence[i - 1] == -1 and i + i - 1 < 2 * N:
            sequence[i - 1] = i
            sequence[i + i - 1] = i
        else:
            return -1
    return sequence

def solve_test_cases(T, test_cases):
    results = []
    for N in test_cases:
        sequence = construct_doubled_sequence(N)
        if sequence == -1:
            results.append("-1")
        else:
            results.append(" ".join(map(str, sequence)))
    return results

# Read input
import sys
input = sys.stdin.read
data = input().split()

T = int(data[0])
test_cases = [int(data[i]) for i in range(1, T + 1)]

# Solve test cases
results = solve_test_cases(T, test_cases)

# Print results
print("\n".join(results))