Playing Doublets with the Primes
I can confirm that the corresponding graph is connected. Moreover, it has a hamiltonian cycle:
For the first question the answer is yes, for the second question the answer is 6,
To solve the question i used both (Java and Wolfram), the idea is this i made a graph with nodes being the primes with 3-digits and there is a line between two nodes iff the primes representing the nodes are 1-Doublet(meaning with one digit change we can transfer one into another) and then we can state you question as graph theory question which are :
1) is the graph connected ?
2) what is the graph diameter ?
building the graph using Java and answering the questions using Wolfram we are done.
it seems that this is true for any number of digits primes, but i don't think there is a simple proof.