How to extract all the diagonal blocks of size 2x2 from NxN matrix?

Suppose we have a square matrix A of size 40 x40 as follow

How to extract all the diagonal blocks of size 2 x 2 from the matrix A ?

Answer 1

[Walter Roberson]

temp = repmat({ones(2,2)}, 1, 20);
L = blkdiag(temp{:});
output = reshape(A(L), 2, 2, []);

This will produce a 2 x 2 x 20 result where each pane is one of the 2 x 2 block diagonals.