Reaction systems are a functional model of interactions between biochemical reactions. They define functions on finite sets (over a common finite domain). In this paper, we investigate combinatorial properties of functions defined by reaction systems. In particular, we provide analytical approximations of combinatorial properties of random reaction systems, with a focus on the probability of whether a system lives or dies. Based on these results, we can create parameterized random reaction

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... ms that rarely die. We also empirically analyze the length of time before such a system enters cyclic behavior, and find that the time is related to the behavior of completely random functions on a smaller domain.