Using numbered variables is a sign that you are doing something wrong.
Putting numbers into variable names like that treats those numbers as pseudo-indices, which are slow, complex, and buggy to work with. It is much simpler to use real indices, which are neat, efficient, and very easy to debug. Unlike what you are trying to do.
Read this to know more:
For example, you could easily use a cell array:
A = cell(1,3);
for k = 1:3
A{k} = B*k + C*k;
end
but probably the best solution would be to learn how to use arrays and write vectorized code. Then you can trivially avoid the loop entirely and write simpler, more efficient code:
V = reshape(1:3,1,1,[]);
A = B.*V + C.*V
