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On the Ramsey Numbers of Certain Graphs of Order Five versus All Connected Graphs of Order Six

Roland Lortz1, Ingrid Mengersen2
1Technische Universitit Braunschweig Diskrete Mathematik 38092 Braunschweig, Germany
2Ostfalia Hochschule fiir angewandte Wissenschaften Fakultat Informatik 38302 Wolfenbiittel, Germany

Abstract

The Ramsey numbers \( r(F, G) \) are investigated, where \( F \) is a non-tree graph of order \( 5 \) and minimum degree \( 1 \), and \( G \) is a connected graph of order \( 6 \). For all pairs \( (F, G) \) where \( F \neq K_5 – K_{1,3} \), the exact value of \( r(F, G) \) is determined. In order to settle \( F = K_5 – K_{1,3} \), we prove \( r(K_5 – K_{1,3}, G) = r(K_4, G) \).

Keywords: Ramsey number, small graph, minimum degree