Fujita et al. [3] introduced the notions of safe number and connected safe number in connection with a variation of the facility location problem. In this paper, we compute the safe number and the connected safe number of Cartesian product of two complete graphs, keywords. Safe set; Connected safe set; Safe number; Connected safe number; Cartesian product; Complete graph.
The work by the first author and the second author was supported by the National Research Foundation of Korea (NRF) funded by the Korea government (MEST) (NRF-2015R1A2A2A01006885) and by the Korea government(MSIP) (NRF-2016R1A5A1008055). The third author's work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2015R1C1A1A01053495).
