O08-105
> restart;with(linalg):
Warning, new definition for norm
Warning, new definition for trace
> a:=n->evalm(matrix(n,n,1)-diag(1$n));a(3);

            a := n -> evalm(matrix(n, n, 1) - diag(1 $ n))


                            [0    1    1]
                            [           ]
                            [1    0    1]
                            [           ]
                            [1    1    0]

> seq([eigenvals(a(n))],n=2..5);

      [1, -1], [2, -1, -1], [3, -1, -1, -1], [4, -1, -1, -1, -1]