Constructs the so called Kac (Clement) (n+1)x(n+1) tridiagonal matrix, defined by: 

| 0, n, 0, ... , 0 | 

| 1, 0, n-1, 0, ..., 0 | 

| 0, 2, 0, n-2, 0, ... | 

| ...........n-1, 0, 1 | 

| 0, ... ........, n, 0| 

The eigenvalues of so defined matrix are 2k-n for k=0,1,2,...,n.

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