I have a big matrix and I have partitioned it. So, I want to say that I am taking the summation of entries that do not belong to the blocks in the diagonal. How can I say it mathematically.
Is it correct to define:
$A = \{(i, j): (i,j) \in \Omega_{kl}, \forall k \neq l; i, j= 1, 2,...p; k, l=1, 2,..., M\}$
M is the total number of blocks. p is the dimension of big matrix which I have partitioned.
Any help is greatly appreciated.