Denver painter Clark Richert is a perennial favorite with young artists, both the many students he's influenced as an art professor at the Rocky Mountain College of Art and Design and others who have taken his lessons through osmosis. Richert is interested in advanced math, which he uses to determine the details of his paintings and other works like "Riemannian Tangercies," his public-art piece in pavement and epoxy that decorates the fire lane at the Museum of Contemporary Art/Denver. That work was closely related to the paintings and digital prints shown at Rule last fall, in which he laid out non-repeating patterns using a range of colors against an indeterminate monochrome ground. An intriguing aspect of Richert's oeuvre is the way he remains loyal to his principles while constantly changing the way his pieces look.