New posts in combinatorics

How many 5-cards poker hands are there containing at least 3 of the 4 suits?

probability combinatorics card-games

A very challenging probability question

probability combinatorics probability-distributions

How many surjective functions are there from $A=${$1,2,3,4,5$} to $B=${$1,2,3$}?

combinatorics functions

Summation with combinations

combinatorics number-theory

Inductive proof for $\binom{2n}{n}=\sum\limits_{k=0}^n\binom{n}{k}^2$

combinatorics summation induction binomial-coefficients

Partitions that separate all subsets

combinatorics extremal-combinatorics

Median of the set of numbers which consists of all positive integers whose digits strictly increase from left to right

Proof of divisibility with combinatorics

combinatorics elementary-number-theory divisibility

Combinatorics - Sets - Min number of items from combinations that, when generated combination os its elements, equals superset

Recurrences for even and odd indexed of Fibonacci Numbers

combinatorics discrete-mathematics generating-functions fibonacci-numbers

How do I determine the number of odd integers in a range?

Number of $r$ - polygons in an $n$ - polygon with no side coinciding

combinatorics geometry combinations

Prove that a field of a set has $2^r$ elements if it has finite cardinality.

combinatorics measure-theory cardinals

Using Burnside's lemma to count number of strings [duplicate]

The number of positive integers less than 1000 with an odd number of divisors

combinatorics elementary-number-theory divisibility

Is there a combinatorial explanation for the identity: $\sum_{k=1}^n c(n,k)2^k = (n+1)!$

Probability of rolling a dice 8 times before all numbers are shown.

probability combinatorics

Find no. of non negative integer solutions of $a+2b+3c = 200$

A nice combinatorial identity: $\sum_{k=1}^{n-1}\frac{\binom{k-1}{n-k-1}+\binom{k}{n-k-1}}{\binom nk}=1$

combinatorics summation binomial-coefficients

Toss 100 fair coins and take away the tails; toss the remaining coins and take away the tails. Continue until no coins remain. [duplicate]

probability combinatorics statistics expected-value