In this note we compute the boundary of some generalized numerical range $W_q(A)$ of a $4 \times 4$ Toeplitz nilpotent matrix $A$. We also provide a program to plot $W_q(A)$ by using ``Mathematica".
The second author was supported in part by Japan Society for the Promotion of Science, KAKENHI, project number 15K04890.
"The boundary of the Q-numerical range of some Toeplitz nilpotent matrix." Nihonkai Math. J. 27 (1-2) 155 - 165, 2016.