  When we study the Karnaugh map in the switching theory course, we learn that
the ones in the map must be combined in groups of $a \times b$ elements, being
$a$ and $b$ powers of two. The result is the logic function described as a sum
of products. This paper shows that we can also make groups where $a$ and/or $b$
are equal to three. This does not result in a sum of products, but in a logic
function that is simpler than the sum of products in terms of logic gates. This
idea is extended later in the paper to groups of $2^n-1$ elements.
