A majority, or a larger or smaller portion or number as provided in the articles or bylaws which in no event shall be less than one-third, of the directors currently holding office is a quorum for the transaction of business at a meeting of the board. 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 a number of directors originally present leaves less than the proportion of number otherwise required for a quorum.