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?

The numbers three, five, and seven are treated in Craft Masonry purely as symbols representing specific ideas rather than as possessing occult or magical virtues 1. Adopted in part through Pythagorean influence regarding the perfection of odd numbers, these numbers structure the symbolic ascent of the Fellowcraft 12.

In the Fellowcraft degree, the number three represents the three principal officers of a lodge—the Worshipful Master, Senior Warden, and Junior Warden—symbolizing the supportive circle of the Fraternity assisting the Mason in his progress, while also making symbolic reference to Deity 2. The number five is concerned with the five orders of architecture and the five human senses 2. The number seven represents the seven Liberal Arts and Sciences 2.

William Preston wrote or adopted the monitorial lectures in which these numbers occur during the latter half of the eighteenth century, presenting them as emblems for enlarging mental horizons and advancing spiritual life 12.