@article { author = {Naji, Ahmed and Davvaz, B. and Mahde, Sultan S. and Soner, N.D.}, title = {A study on some properties of leap graphs}, journal = {Communications in Combinatorics and Optimization}, volume = {5}, number = {1}, pages = {9-17}, year = {2020}, publisher = {Azarbaijan Shahid Madani University}, issn = {2538-2128}, eissn = {2538-2136}, doi = {10.22049/cco.2019.26430.1108}, abstract = {In a graph $G$, the first and second degrees of a vertex $v$ are equal to the number of their first and second neighbors and are denoted by $d(v/G)$ and $d_2(v/G)$, respectively. The first, second and third leap Zagreb indices are the sum of squares of second degrees of vertices of $G$, the sum of products of second degrees of pairs of adjacent vertices in $G$ and the sum of products of first and second degrees of vertices of $G$, respectively. In this paper, we initiate in studying a new class of graphs depending on the relationship between first and second degrees of vertices and is so-called a leap graph. Some properties of the leap graphs are presented. All leap trees and $\{C_3, C_4\}$-free leap graphs are characterized.}, keywords = {Distance-degrees (of vertices),leap Zagreb indices,leap graphs}, url = {http://comb-opt.azaruniv.ac.ir/article_13876.html}, eprint = {http://comb-opt.azaruniv.ac.ir/article_13876_3e34a313e1c9a12cdfc1edc950e25098.pdf} }