Department of Mathematical Sciences, University of Puerto Rico, Mayaguez, USA. Department of Mathematics, Taiyuan Normal University, Taiyuan, China. Department of Mathematics, Yili Normal University, ...

ABSTRACT: In this note, we show that the number of digraphs with n vertices and with cycles of length k, 0 ≤ k ≤ n, is equal to the number of n × n (0,1)-matrices whose eigenvalues are the collection ...