Kragujevac J. Math. 26 (2004) 15-18.

ANOTHER CLASS OF EQUIENERGETIC GRAPHS

Harishchandra S. Ramane,1 Ivan Gutman, 2
Hanumappa B. Walikar,3 Sabeena B. Halkarni3

1Department of Mathematics, Gogte Institute of Technology, Udyambag, Belgaum - 590008, India
(e-mail: hsramane@yahoo.com)
2Faculty of Science, P. O. Box 60, 34000 Kragujevac, Serbia & Montenegro
(e-mail: gutman@knez.uis.kg.ac.yu)
3Department of Mathematics, Karnatak University. Dharwad - 580003, India
(e-mail: walikarhb@yahoo.co.in  ;  sabeena h@yahoo.com)

Abstract. The energy of a graph is the sum of the absolute values of its eigenvalues. Let G and L2(G) denote the complement and the second iterated line graph, respectively, of the graph G. If G1 and G2 are two regular graphs, both on n vertices, both of degree r ³ 3 , then L2(G1) and L2(G2) have equal energies, equal to (nr - 4)(2r - 3) - 2.