From the Muppet Wiki:

“Geometry of Circles” is a series of unnumbered animation pieces created for Sesame Street in 1979 with music by Philip Glass.

The shorts consist of the movement of six circles (each with a different color of the rainbow) that are formed by and split up into various geometric patterns. Glass’s music underscores the animation in a style that closely resembles the “Dance” numbers and the North Star vignettes written during the same time period as his Einstein on the Beach opera.