def generate_doubled_sequence(N):
    if N % 2 != 0:
        return "-1"
 
    sequence = [0] * (2 * N)  # Create an array of size 2N
 
    # Place numbers from N down to 1
    for i in range(N, 0, -1):
        first_position = i - 1  # 0-indexed position for the first occurrence
        second_position = first_position + i  # 0-indexed position for the second occurrence
 
        sequence[first_position] = i
        sequence[second_position] = i
 
    return ' '.join(map(str, sequence))
 
def main():
    import sys
    input = sys.stdin.read
    data = input().strip().split()
 
    T = int(data[0])  # Number of test cases
    results = []
 
    for i in range(1, T + 1):
        N = int(data[i])
        results.append(generate_doubled_sequence(N))
 
    print("\n".join(results))
 
if __name__ == "__main__":
    main()

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