A prime $p$ is in class $1$ if the only prime divisors of $p+1$ are $2$ or $3$. In general, a prime $p$ is in class $r$ if every prime factor of $p+1$ is in some class $\leq r-1$, with equality for at least one prime factor. Show that for each $r$ there exists a prime $p$ of class $r$.

How a contribution reaches this record

Seven steps, in four places.

1. 1

   Read the sources and their formal declarations.

   Public
2. 2

   Work on it, wherever you work.

   Your machine
3. 3

   Keep an Approach and its Attempts here.

   Needs an account
4. 4

   Attach evidence by its content root.

   Needs an account
5. 5

   Prepare an unsigned Submission draft.

   Needs an account
6. 6

   Sign it with your own key.

   Your machine
7. 7

   The Repository decides.

   The Repository