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   on graphs with integer sombor indices  
   
نویسنده sepehr marzie ,jafari rad nader
منبع communications in combinatorics and optimization - 2024 - دوره : 9 - شماره : 4 - صفحه:693 -705
چکیده    ‎sombor index of a graph $g$ is defined by $so(g) = sum_{uv in e(g)} sqrt{d^2_g(u)+d^2_g(v)}$, where $d_g(v)$ is the degree of the vertex $v$ of $g$. an $r$-degree graph is a graph whose degree sequence includes exactly $r$ distinctive numbers. in this article, we study $r$-degree connected graphs with integer sombor index for $r in {5, 6, 7}$. we show that: if $g$ is a 5-degree connected graph of order $n$ with integer sombor index then $n geq 50$ and the equality occurs if only if $g$ is a bipartite graph of size 420 with $so(g) = 14830$; if $g$ is a 6-degree connected graph of order $n$ with integer sombor index then $n geq 75$ and the equality is established only for the bipartite graph of size $1080$; and if $g$ is a 7-degree connected graph of order $n$ with integer sombor index then $n geq 101$ and the equality is established only for the bipartite graph of size $1680$.
کلیدواژه integer sombor index; bipartite graphs; r-degree
آدرس shahed university, department of mathematics, iran, shahed university, department of mathematics, iran
پست الکترونیکی n.jafarirad@gmail.com
 
     
   
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