8505402751domain: NAppears in sequencesPrime numbers p where d(p-1) = d(p+1) increases to a record.at n=20A190821Primes p such that min(d(p-1), d(p+1)) is larger than the corresponding values of all previous primes, where d(n) is the number of divisors of n (A000005).at n=33A319823