Quartet
See also
Hexad, Monad, Quintet, Tetrad, TriadExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Quartet." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Quartet.html
Weisstein, Eric W. "Quartet." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Quartet.html