I'm facing this sum of products $\sum_{j, k=1; j\neq k}^{3}\theta_j \theta_k$.
Now, does this mean
${1\times2 + 1\times3 + 2\times1 + 2\times3 + 3\times1 + 3\times2}$
or just
${1\times2 + 1\times3 + 2\times3}$?
Thanks.
Asked
Active
Viewed 34 times
0
-
Are you sure there's a $g$ in the formula? – Daniel Robert-Nicoud Oct 29 '17 at 13:14
-
The first, after putting in the $\theta$'s. – Ethan Bolker Oct 29 '17 at 13:16
-
The $g$ is in the formula, I just added the $=3$ to signal that it goes from $1$ to $3$. – jay.sf Oct 29 '17 at 13:16
-
okay, I've edited accordingly, now it should be clearer. – jay.sf Oct 29 '17 at 13:18
-
1Assuming your numbers refer to the indices of $\theta$ then it is the top one. There is no restriction of the form $j<k$. – lulu Oct 29 '17 at 13:26
-
@lulu Yes they do. Okay thanks, that's what I thought. Hopefully the author used the formula accurately. – jay.sf Oct 29 '17 at 13:29