[seqfan] Re: A058054

[Hans Havermann]

Frank Adams-Watters:

> If p is a prime, there is some ambiguity as to whether prevprime(p) is p, or the prime before p. (Similarly for nextprime, of course.) PARI definitely returns p for these; I think Mathematica does, too.

In Mathematica, NextPrime[n] is strictly the prime above n. PreviousPrime[n] was a Mathematica add-on once upon a time. It was never built-in, which is why you see it user-defined in OEIS Mathmatica code that implements it.