Problem With Sum I would like help with the following summation. Every time I come to this step in my signals class, I have difficulty proving that:
$$
\sum_{j=0}^{n-3}1=n-2
$$

The pattern is simple:
Let $S_n:=\sum_{j=0}^{n-3}1$. We have
$$S_3=1_0=1,\\S_4=1_0+1_1=2,\\S_5=1_0+1_1+1_2=3,\\S_6=1_0+1_1+1_2+1_3=4,\\\cdots$$
(the indices are there to explicit the values of $j$).
