Okla. Stat. tit. 18, § 18-907: Board of directors

The business and affairs of a corporation shall be conducted by

a board of directors. The number of directors shall be a multiple

of three with a minimum of fifteen and a maximum of twenty-one. Two-

thirds of the directors shall be elected by the members, and one-

third shall be elected by the stockholders. One-third of the

original board shall be elected for a term of one (1) year, one-

third for a term of two (2) years, and one-third for a term of three

(3) years; all directors subsequently elected shall serve for a term

of three (3) years. Any vacancy in the office of a director elected

by the members shall be filled by the directors elected by the

members, and any vacancy in the office of a director elected by the

stockholders shall be filled by the directors elected by the

stockholders.