def construct_doubled_sequence(N):
    if N % 2 == 1:
        return "-1"  # No valid sequence for odd N
 
    # For even N, construct the sequence
    sequence = []
    for i in range(1, N + 1):
        sequence.append(i)
        sequence.append(i)
 
    # We need to rearrange to satisfy the distance condition
    # A simple method is to interleave the pairs
    result = []
    for i in range(1, N + 1):
        result.append(i)
        result.append(i)
 
    # A pattern to ensure that it meets the doubled condition
    # Let's rearrange it as:
    for i in range(1, N + 1):
        result[i - 1], result[2 * i - 1] = result[2 * i - 1], result[i - 1]
 
    return ' '.join(map(str, result))
 
def main():
    import sys
    input = sys.stdin.read
    data = input().strip().split()
 
    T = int(data[0])
    results = []
    for i in range(1, T + 1):
        N = int(data[i])
        results.append(construct_doubled_sequence(N))
 
    print('\n'.join(results))
 
if __name__ == "__main__":
    main()
 

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