Can you elaborate as an expert in Esoterism on the symbolic meaning of the masonic years 3, 5 and 7 in the blue lodge setting?

Numbers in Craft Masonry function purely as symbols representing specific moral and intellectual concepts rather than possessing occult or magical virtue 2. The sequence of three, five, and seven appears in the Fellowcraft Degree, specifically embodied in the steps of the winding stairs leading to the Middle Chamber 23.

The number three refers to the three principal officers of a lodge—the Worshipful Master, Senior Warden, and Junior Warden—who govern the body 3. Symbolically, three points to Deity, traditionally symbolized by the triangle, and serves to remind the candidate that he does not make his progress alone but is supported by the entire Fraternity 3. In the broader system of the lodge, three also represents the Three Grand Pillars of Wisdom, Strength, and Beauty 1.

The number five is associated with the five orders of architecture—Doric, Ionic, Corinthian, Tuscan, and Composite—as well as the five human senses 13.

The number seven refers to the seven Liberal Arts and Sciences: grammar, rhetoric, logic, arithmetic, geometry, music, and astronomy 3.

Carl Claudy notes that this step-by-step progression represents a candidate's mental and spiritual elevation, encouraging the expansion of his intellectual horizons and moral outlook 3. Albert Mackey emphasizes that William Preston arranged or adopted these monitorial lectures in the late eighteenth century, intending them purely as rational and allegorical tools for moral instruction rather than mystical numerology 2.