Fourth-year math major Benjamin Liu, from Northampton, Mass., has broken the Celtic knot into 12 standard segments that can be rearranged to create variations of the interlacing, decorative strands.

The Celtic knot — a pattern of interlocking lines — is centuries old, carved into ancient stones all over Ireland. But that tattoo on your biceps? Like the fortune cookie, American born and bred.

The hypnotic Celtic knot might not be as complicated as it seems. Fourth-year math major Benjamin Liu, from Northampton, Mass., has broken the Celtic knot into 12 standard segments that can be ...