Project Euler Forum

I am sorry if I am just misunderstainding, but doesn't the problem statement need some information on distinctness of coins?
Without information, shouldn't F(3, 2) equal to 2 instead of 4? - HHH or TTH.
Since they are arranged in a circle, TTH, HTT, THT should all be identical. To obtain the assumed correct value, I think the coins should be numbered 1 to n and first arranged in this order clockwise in a circle... or something like that, though the expected condition is deduced from test cases.

Just being curious after having more than 100 solvers:
is there a plan to adjust the difficulty of this problem?

10 weeks after publication a problem is moved from recent problems to the archives.
At that moment a difficulty assessment is automatically calculated.
If there are less than 100 solvers the assessment is temporary.

Thanks for the clarification, though I was aware of the regular calculation method.
I asked my previous question because this problem - if one only checks the fastest solver's table - seems more difficult than it actually is since there was no correct answer in the first 7 hours.
But as far as I understood there won't be any manual adjustments in the final difficulty calculation.

You're right.
However, after the correct answer was on the site the number of correct answers grew rather fast.
The difficulty is measured as the speed of solutions not the number of them.