<we><edit> <!-- questions and answers -->
algebraic-topology
derivatives
convex-analysis
differential-topology
calculus
contest-math
pde
numerical-methods
recurrence-relations
abstract-algebra
algebra-precalculus
exponential-function
combinations
proof-writing
general-topology
fourier-analysis
hilbert-spaces
algorithms
random-variables
algebraic-geometry
prime-numbers
set-theory
sequences-and-series
asymptotics
manifolds
combinatorics
Permutation of different coloured balls
combinatorics
permutations
Number of binary strings not having even-length runs of $0$ or $1$
combinatorics
permutations
fibonacci-numbers
binary
Number of divisors of the number $2079000$ which are even and divisible by $15$
combinatorics
permutations
Shortest Addition Chain to Arrive to $100$
combinatorics
numerical-methods
computer-science
How many ways can hexagonal tiles of side a be arranged in a b*a sided triangle?
combinatorics
combinations
combinatorial-geometry
tiling
Find a distribution and probability.
probability
combinatorics
proof-verification
Combinatorics: choose 10 mathematicians out of $18$ mathematicians and $6$ physicists out of $12$ physicists.
combinatorics
combinations
How many ways to add to $50$ with $1, 4$ and $6$
combinatorics
Proof: Generalized Version Of The Basic Counting Principle
combinatorics
Number of Multiples of $a+bi \in \mathbb{Z}[i]$ with bounded norm
abstract-algebra
combinatorics
gaussian-integers
Number of ways I can create positive 5-number integers (which are multiples of 5)
combinatorics
Logic using Permutation
combinatorics
permutations
Give a combinatorial proof for the identity
combinatorics
combinatorial-proofs
What is the $n$-th difference of $\sin(ax)$
calculus
combinatorics
recurrence-relations
Number of ways 6 things can be selected from a group of identical things
combinatorics
combinations
Number of graphs on [100n] vertices with degree at most 100
combinatorics
graph-theory
Calculating entropic penalties based on combinatorics
probability
combinatorics
The number of words (finite sequences) up to isomorphism
combinatorics
My Simple Combinatorial Method to Enumerate All Sudoku Solution Grids
combinatorics
puzzle
sudoku
Subgroups of $PSL(2,q)$
combinatorics
group-theory
geometry
differential-geometry
finite-groups
Colored ball problem combinations distribution
probability
combinatorics
combinations
Prove by a combinatorial argument that ${n \choose r}{r \choose s}={n \choose s} {n-s \choose r-s} $
combinatorics
Probability: Find the number of ways to select $5$ clerks from $20$ applicants.
combinatorics
binomial-coefficients
Prove by a combinatorial argument that $(n-r){n \choose r}=n{n-1 \choose r}$
combinatorics
combinations
combinatorial-proofs
In how many ways can one yellow, two red and four green beads be placed on a bracelet if the beads are identical apart from colour?
combinatorics
permutations
Beggar-my-neighbour possible games
probability
combinatorics
algorithms
permutations
card-games
How many samples of size $4$ selected from $10$ red and $5$ white numbered marbles have exactly $3$ red marbles?
combinatorics
combinations
Determine remainder when N is divided by 1000?
combinatorics
contest-math
combinations
Combinatorics intuition
combinatorics
Ensuring the Multinomial Counting Theorem Produces Integer Coefficients
combinatorics
Number of Unique Positive Integer Solutions
combinatorics
number-theory
How many combinations of $n$ balls of up to $n$ different colors are there?
combinatorics
combinations
Simplification of a Finite Sum
probability
sequences-and-series
combinatorics
multisets
How many distinct games are there on a set of cards?
combinatorics
discrete-mathematics
elementary-set-theory
find $\sum_{k=0}^{n}(-1)^k\binom{n}{k}^2$
combinatorics
summation
binomial-theorem
In how many ways can we to place an $X$ in four cells, such that there is exactly one $X$ in each row, column, and $2\times2$ outlined box?
combinatorics
sudoku
How many sets of numbers can we find?
combinatorics
combinations
How many ways can I put down two indistinguishable pieces on an ordinary $8 \times 8$ chessboard if they must either be in the same row or column?
combinatorics
chessboard
How many symmetric oriented graphs with n vertices are there?
combinatorics
matrices
graph-theory
induction
Ways of choosing ice-cream scoops - intuition/further explanation
combinatorics
binomial-coefficients
binomial-theorem
Comparing Binary Matrices and Weights
combinatorics
matrices
computer-science
binary
A seemingly simple composite induction (pun intended)
combinatorics
induction
Permutations of Subsets of a Multiset
combinatorics
multisets
A general solution for the probability of getting at least $k$ out of $n$ total distributed objects
probability
combinatorics
How many combinations of couples sitting on a roundtable?
combinatorics
combinations
Given is a binary relation. Determine the Hasse diagram for it and two upper bounds
combinatorics
discrete-mathematics
graph-theory
relations
order-theory
Prove that no set of $n$ points can be triangulated in more than $2^{n \choose 2}$ ways.
combinatorics
algorithms
computational-geometry
triangulation
Why does raising this polynomial to a power, give the correct answer for a combinatorics problem?
combinatorics
polynomials
exponentiation
Maximum of minimum number of moves required for hardest 8 puzzle
combinatorics
puzzle
searching
Find the number of arrangements that can be made of the letters of the word 'DIFFERENT' without changing the place of a vowel?
combinatorics
permutations
Method for approaching combinatorial proofs
combinatorics
Finding the numbers having a particular factor,an upper limit and a specific set of digits.
combinatorics
Prove using mathematical induction
combinatorics
induction
Similar sequences of coin flips
combinatorics
Prove that in a 10-element subset of $\{1, \dots , 50 \} $ there exist 2 $5$-element subsets such that the sums of all their elements are equal.
combinatorics
elementary-number-theory
Find the number of ways of arranging the letters
combinatorics
permutations
Combinatorics: If my phone has a $5$-pin code to unlock it but I only remember $3$ digits, what are the outcomes?
combinatorics
permutations
The number of ways in which 10 identical apples can be distributed to six children so that each child receives at least one apple
combinatorics
combinations
The number of ways in which 5 different books can be given to 10 people with a condition
combinatorics
combinations
Combinatorial proof for a Sterling identity
combinatorics
discrete-mathematics
stirling-numbers
Combinatorial Summation proof
combinatorics
Proving using mathematical induction
combinatorics
induction
Permutation: Number of ways 4 cars could park
combinatorics
permutations
Summation of combinations upto a specified bound
combinatorics
combinations
Application of multinomial theorem in combinatorics
combinatorics
How many ways are there to form a 16-digit number in which each digit appears at least once
combinatorics
Combinatorics : Circular Permutation of N people with N-1 spots
probability
combinatorics
permutations
combinations
How many $10$ digit numbers containing $1$, $3$, $5$, $7$ and $9$ are there?
combinatorics
Probability that m samples without replacement cover the entire set
probability
combinatorics
sampling
Countdown maths puzzle with a twist - ?multiset combinations with repetition?
combinatorics
permutations
combinations
multisets
Combination from arbitrary number of type of items
probability
combinatorics
combinations
A power series = golden ratio = sin of arcsin formulae?!
combinatorics
power-series
golden-ratio
catalan-numbers
Number of vectors with the same $i$-th entry
linear-algebra
combinatorics
vector-spaces
How does probability rate increase in this situation?
probability
combinatorics
combinations
What is the generating function for the number of Multisets
combinatorics
generating-functions
Is this correct: Inflection points of Euler number graph in Island-Mainland transition correspond to spanning cluster site percolation threshold?
probability
combinatorics
graph-theory
percolation
Find $\sum_{n=1}^{10^6}\lfloor\sqrt n\rfloor$.
combinatorics
summation
floor-function
Average vector norm after 'dropping' a few dimensions
combinatorics
vectors
norm
Zip Code Combinations
combinatorics
In how many ways can you put two people in $5$ seats in a row if they cannot sit together?
combinatorics
permutations
combinations
Question about the proof of the Mobius function for the lattice of subspaces
combinatorics
lattice-orders
mobius-function
mobius-inversion
What is the ratio of the number of ways to represent a number with a sum of $k$ numbers?
combinatorics
A homework problem about set theory
combinatorics
set-partition
Formation of a 7 digit number using 3 digits with given condition
combinatorics
permutations
How many permutations of 160 outputs from binomial B(1, p) if p varies?
combinatorics
probability-distributions
Phase 10 probabilities
probability
combinatorics
combinations
Calculating the probability of being dealt a straight in the Phase 10 card game
probability
combinatorics
combinations
Horse race combinations when ties are allowed
combinatorics
Looking to get a handle on SSCG(3) (which is much, much larger than TREE(3))
combinatorics
graph-theory
If I have a certain word, how can I find the lowest number of characters that must remain in their original spots if I permute it?
combinatorics
permutations
combinatorics-on-words
Fibonacci and Lucas series technique
sequences-and-series
combinatorics
fibonacci-numbers
lucas-numbers
Completely marked squares in squares
combinatorics
pigeonhole-principle
Picking a sample of N numbered balls
probability
combinatorics
Is there some combinatorial intuition behind generating functions of sequences?
combinatorics
Neighbor-difference permutations
combinatorics
Combinations question - why is my approach wrong?
combinatorics
Number of colourings for which the vertices of a square can be coloured by three different colours such that adjacent vertices get different colours.
combinatorics
coloring
How many permutations avoid previous adjacencies?
combinatorics
If $A$ is the alternating operator, prove that $A(A(\omega\otimes\eta)\otimes\nu)=A(\omega\otimes\eta\otimes\nu)$
combinatorics
group-theory
permutations
tensor-products
symmetric-groups
Calculating the Shapley value in a weighted voting game.
combinatorics
binomial-coefficients
game-theory
combinatorial-game-theory