How is whether or not coins are stackable determined? I figured that, for the assembly of the first n1 coins to be stackable on the nth coin, the center of mass of the first n1 coins should lie within the nth coin. Knowing the nth center of mass thus gives a quick way to compute the nth angle. It seems natural to store the center of mass in polar coordinates. I found a more or less closed form solution for the radius, as well as an iterative solution, and a formula for the angle of the center of mass and rotation angle in terms of the radius.
But my concern is twofold. My formulae seem a little bit off: the total angles for the numbers of coins given are about 3% off, but the error decreases for more coins. I know there is probably a precision problem as well. Unfortunately I haven't been able to find any clean form for the sum of angles. Have others used a laurent series or some other approximation?
I won't put my exact formula for the radius, but the n=2 radius can be immediately calculated assuming the center of mass interpretation is correct.
Problem 737
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Problem 737
Last edited by hacatu on Wed Dec 09, 2020 8:13 pm, edited 1 time in total.

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Re: Problem 737
It's very early to post values hacatu. Please keep working on the problem and remove the values. Possibly, someone will reply and you can get the chat in a private forum.
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Re: Problem 737
I don't think you should be concerned about that, as long as it's 3% over rather than 3% under. Bear in mind that those numbers given are for the first point at which a discrete number of coins passes the nth full rotation. There's no expectation that they should exactly overlap.