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The Turán number of a graph H, ex(n,H), is the maximum number of edges in an n-vertex graph that does not contain H as a subgraph. Let Pk denote the path on k vertices and let Sm i=1 Pki denote the disjoint union of Pki for 1 ≤ i ≤ m; in particular, write Sm i=1 Pki = mPk if ki = k for all 1 ≤ i ≤ m. Yuan and Zhang determined ex(n, Sm i=1 Pki ) for all integers n if at most one of k1, . . . , km is odd. Much less is known for all integers n if at least two of k1, . . . , km are odd. Partial results such as ex(n,mP3), ex(n, P3 ∪ P2ℓ+1), (n, 2P5), ex(n, 2P7) and ex(n, 3P5) have been established by several researchers. In this paper, we develop new functions and determine ex(n, 3P7) and ex(n, 2P3 ∪ P2ℓ+1) for all integers n. We also characterize all the extremal graphs. Both results contribute to a conjecture of Yuan and Zhang. © 2024 University of Zielona Gora. All rights reserved.
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Discussiones Mathematicae - Graph Theory
ISSN: 1234-3099
Year: 2024
Issue: 4
Volume: 44
Page: 1513-1537
0 . 5 0 0
JCR@2023
Cited Count:
SCOPUS Cited Count: 2
ESI Highly Cited Papers on the List: 0 Unfold All
WanFang Cited Count:
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30 Days PV: 1
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