Pile of Coins

Making a pile of n coins with a radius of R. Each of the coins is placed so that the center point of the coin is slightly to the right of the coin underneath it. How many coins at least are needed so that seen directly from above, the top coin and the bottom coin don't overlap at all? With n coins available, how far to the right from the bottom coin can the top coin be without making the pile collapse?

Originally posted by talzamir
Making a pile of n coins with a radius of R. Each of the coins is placed so that the center point of the coin is slightly to the right of the coin underneath it. How many coins at least are needed so that seen directly from above, the top coin and the bottom coin don't overlap at all? With n coins available, how far to the right from the bottom coin can the top coin be without making the pile collapse?

5 coins such that the bottom and top coin don't overlap at all, and with n coins available, the distance the top could be from the bottom is infinite as the harmonic series is divergent.