Eisenstein Unit

The Eisenstein units are the Eisenstein Integers $\pm 1$, $\pm\omega$, $\pm\omega^2$, where

$$\omega = {\textstyle{1\over 2}}(-1+i\sqrt{3}\,)$$

$$\omega^2 = {\textstyle{1\over 2}}(-1-i\sqrt{3}\,).$$

See also Eisenstein Integer, Eisenstein Prime

References

Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, pp. 220-223, 1996.