I've seen two different versions of how you can move from one prime to another: Version 1: change a single digit Version 2: change a single digit and then permute the digits subject in both cases to the restriction that the new prime cannot begin with 0; the number of digits must remain constant. Call two primes equivalent if you can go from one to the other in this way. For each version of equivalence, there are four obvious sequences: a(n) = number of equivalence classes of primes with n digits. Arrange the equivalence classes by the size of the smallest member. b(k) = size of the k-th equivalence class c(k) = smallest member of the k-th equivalence class d(k) = largest member of the k-th equivalence class Presumably the two a-sequences will begin with a bunch of 1's, the two b-sequences will start like A006879, the two c-sequences will start like A003617, and the two d-sequences will start like A003618. There are potentially eight (new?) sequences here - could someone compute them? Thanks! Neil