def aai2nti(i):
    """
    # nt index is 0-based
    # aa index is 1-based
    # test 
    # dict(zip(range(1,60),[aai2nti(i) for i in range(1,60)]))
    """
    return [(i - 1) * 3, (i - 1) * 3 + 1, (i - 1) * 3 + 2]
