On Turán number for Sℓ1∪Sℓ2
On Turán number for Sℓ1∪Sℓ2
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DOI：
10.1016/j.amc.2020.125400
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
Jia-Yun Li;Sha-Sha Li-Sha;Jianhua Yin
中科院分区：
文献类型：
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作者：
Jia-Yun Li;Sha-Sha Li-Sha;Jianhua Yin
The Turán number of a graph G, denoted by ex (n, G), is the maximum number of edges of an n-vertex simple graph having no G as a subgraph. Let S ℓ denote the star on ℓ+ 1 vertices. In this paper, we investigate to determine the Turán number for S ℓ 1∪ S ℓ 2, where ℓ 1> ℓ 2. We give a new lower bound on e x (n, S ℓ 1∪ S ℓ 2). Moreover, if ℓ 2+ 1≤ ℓ 1≤ 2 ℓ 2+ 1 (or if ℓ 1≥ 3 and ℓ 2= 2), we determine the exact values e x (n, S ℓ 1∪ S ℓ 2) for all positive integers n (or for almost all positive integers n), which improves two results of Lidický et al.
