On an arithmetic function considered by Pillai
Florian Luca, Ravindranathan Thangadurai (2009)
Journal de Théorie des Nombres de Bordeaux
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For every positive integer let be the largest prime number . Given a positive integer , we study the positive integer such that if we define recursively for , then is a prime or . We obtain upper bounds for as well as an estimate for the set of whose takes on a fixed value .