For questions about the study of finite or countable discrete structures, specifically how to count or enumerate elements in a set (perhaps of all possibilities) or any subset. It includes questions on permutations, combinations, bijective proofs, and generating functions. Combinatorics is a ...

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13
votes
1answer
238 views
+50

Is it possible to uniquly number faces of a hexagonal grid with consecutive numbers

You have a grid of regular hexagons. The aim of the game is to have each hex contain the numbers 1-6 on its edges. Each edge must also be connected to another edge that has a value one higher and ...
4
votes
2answers
335 views
+100

Probability of some die face being missed N or more times in a row in M rolls?

Say I have a (fair) die with $F$ faces. I roll it $M$ times. How can I calculate the probability that some face was not seen for $N$ or more in a row of the $M$ rolls? (any face, not just a specific ...
8
votes
1answer
110 views
+50

A set of integers whose elements all divide $2015^{200}$ but do not divide each other

Let $S$ be a set of natural numbers,such that each element divides $2015^{200}$ but for no two elements $a$ and $b$, $a|b$. Find the maximum number of elements in $S$ . $2015^{200}=(5\cdot ...