New posts in combinatorics

How many such different permutations? [duplicate]

Maximal cardinality of Sidon set

Using two coins to select a person fairly.

Closed form of factorial and cascading power sum

Minimum number of subsets of $A$ of a given order that contain all possible pairs of elements of $A$

How many arrangements of the letters in the word CALIFORNIA have no consecutive letter the same?

The set $S=\{a+1,a+2, a+3,\dots,a+2015,a+2016\}$ with exactly 20 primes

When does the game end?

What is the maximal number of subsets of a finite set, such that no one is the unions of some other ones? [closed]

$S$ be a collection of subsets of $\{1,...,100\}$ ; any two sets in $S$ has non-empty intersection , what is the maximum possible value of $|S|$?

How many different game situations has connect four?

How many strings of four decimal digits do not contain the same digit twice?

What is the probability that the expectation value is the actual value in this experiment

Sum of 1.5-powers of natural numbers

Show that $\frac1{\sqrt{(n+\frac12) \pi}} \le\frac{1\cdot 3\cdot 5 ... (2n-1)}{2\cdot 4\cdot 6 ... (2n)} \le \frac1{\sqrt{n \pi}} $

Palindrome Subtraction

Placing a kth adjacent term in a row of k-1 non-adjacent terms

A combinatorics problem related to Bose-Einstein statistics

Show that ${{2m} \choose {m}} \leq \frac{2^{2m}}{\sqrt{2m}}$.

An old and interesting problem in combinatorics from Russia Mathematics Olympiad