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Before I pose my question I just want to note that I know that this question here been asked here before but the responses were only partially helpful.

A total of $2n$ people, consisting of $n$ married couples, are randomly seated (all possible orderings being equally likely) at a round table. Let $C_i$ denote the event that the members of couple $i$ are seated next to each other, $i = 1, ... , n$.

$(a)$ Find $P(C_i)$.

$(b)$ For $j \neq i$, find $P(C_j|C_i)$.

$(c)$ Approximate the probability, for $n$ large, that there are no married couples who are seated next to each other.

The answer for $(a)$ is $\frac{2}{2n-1}$ and for $(b)$ $\frac{2}{2n-2}$. Allegedly, the answer for $(c)$ is approximately $e^{-1}$ and one acquires that result via Poisson approximation but I am not convinced of this since we're not considering independent trials here. Admittedly, dependence appears to be quite weak but how do I know that it is negligible?

Edit: Perhaps my take on it makes no sense, but I need help solving (c) which is what I was trying to say.

David
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    The argument that they are asymptotically independent isn't entirely valid. For a totally rigorous argument, you can use inclusion/exclusion to calculate the probability exactly and squeeze this probability between two sequences converging to $1/e$, as in here: http://math.stackexchange.com/a/469348/215322 – Marcus M Dec 15 '16 at 00:28
  • That looks headache inducing. I might get around to reading it tomorrow. Thank you for the response. – David Dec 15 '16 at 01:16

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