A majority, or a larger or smaller proportion or number provided in the articles or bylaws but not less than one-third, of the directors currently holding office is a quorum for the transaction of business. In the absence of a quorum, a majority of the directors present may adjourn a meeting from time to time until a quorum is present. If a quorum is present when a duly called or held meeting is convened, the directors present may continue to transact business until adjournment, even though the withdrawal of directors originally present leaves less than the proportion or number otherwise required for a quorum.