On Fri, 2021-02-19 at 15:33 +0100, Martin Bright wrote: > Proof: It's enough to prove it in the case h = (2 4 6 .. n n-1 ... 5 > 3) in cycle notation. Is it? It depends whether 'Plain Bob Lead Heads' means all of them. It's not true for methods with a 1-lead course, but what if n-1 is not prime? PABS