Quintillions. $25 (Maryland residents add $1.25). Available by mail from Kadan Enterprises, Inc., 1227 Lorene Dr., Suite 16, Pasadena, Md. 211229 301/437-2163.

Quintillions is, first of all, a game. But there are four ways to play it, so far. Quintillions is also a puzzle (actually, innumerable puzzles). It also teaches an elementary lesson in geometry and serves as a free form sculpture. All in one. First, the geometry lesson. The idea for Quintillions sprang from a puzzle form in Arthur C. Clarke's science fiction thriller Imperial Earth . Two maryland residents, Kathy Jones and Don Burnham, became fascinated with Clarke's use of quints, which are the twelve possible ways to combine five squares in the same plane. For years quints have been the subject of mathematical pazzles, the kind that Scientific American baffles its readers with each month. But Jones and Burnham say moreto quints than just puzzles, and began experimenting with playing strategies using the quints as cubes. "We focused on building and making a close fit in a sculpture that grows between the players," explains Burnham. The result is Quintillions, a set of laser-cut hardwood blocks and a 48-page rule book that explains how to play the four quints games (or solitaire) and how to build them into shapes. In still another twist of their versatility, the Quintillions blocks also double as free-form desk or table decorations.