Question

What is the number of arrangements in the word "DAUGHTER" where vowels are never together?

score 4k · Answer 1 · 2026-03-27 12:03:10

4k

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What is the number of arrangements in the word "DAUGHTER" where vowels are never together?

Published on 27 Mar 2026 - 12:03

score 182 · Answer 2 · 2026-03-25 13:20:58

182

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Problem concerning the use of Pigeonhole (Box) principle

Published on 25 Mar 2026 - 13:20

score 87 · Answer 3 · 2026-03-26 07:35:31

87

Views

Prove the identity $ \sum\limits_{i=0}^{n} (-1)^{i} (a+2i) \binom{n}{i} \binom{a+n+i}{n+1}^{-1}=(n+1) \delta_{a,0}$

Published on 26 Mar 2026 - 7:35

score 65 · Answer 4 · 2026-03-25 16:03:49

65

Views

How to find the number of elements which share all the characteristics when there are many sets?

Published on 25 Mar 2026 - 16:03

score 182 · Answer 5 · 2018-02-24 19:39:57

182

Views

Counting the sets with elements satisfying $k_i\ge0$, $\sum_i k_i=K$, $\sum_i i k_i=N $.

Published on 24 Feb 2018 - 19:39

score 243 · Answer 6 · 2026-03-22 07:00:06

243

Views

A bijection between Motzkin paths and 3-colored signed Dyck path homomorphs

Published on 22 Mar 2026 - 7:00

score 65 · Answer 7 · 2026-04-02 15:01:16

65

Views

Looking for a challenging task or variant related to the knight's tour problem

Published on 02 Apr 2026 - 15:01

score 113 · Answer 8 · 2026-04-02 12:22:25

113

Views

Bitstrings of length n which the first three bits are not equal using complement

Published on 02 Apr 2026 - 12:22

score 30 · Answer 9 · 2026-04-02 12:21:20

30

Views

What does this count?

Published on 02 Apr 2026 - 12:21

score 179 · Answer 10 · 2026-03-22 11:26:18

Let $L$ be a latin square whose entries are $L_{ij} = i+j (mod n)$. Then there are no $n$ distinct entries from unique rows and columns of $L$

score 102 · Answer 11 · 2018-02-25 00:47:14

A committee of 4 is to be formed out of 6 superheroes, 7 supervillains, and 4 citizens. How many ways to form a committee?

score 80 · Answer 12 · 2026-03-25 03:02:12

80

Views

Evaluating a Difference Operator of a Product of Factorial Polynomials

Published on 25 Mar 2026 - 3:02

score 445 · Answer 13 · 2026-03-26 09:48:00

445

Views

Bitstrings of length n that do not contain the substring 10

Published on 26 Mar 2026 - 9:48

score 417 · Answer 14 · 2026-03-25 05:46:58

417

Views

How was the integral formula for the binomial coefficient discovered?

Published on 25 Mar 2026 - 5:46

score 254 · Answer 15 · 2026-04-01 14:23:57

254

Views

Number of ways to take parentheses

Published on 01 Apr 2026 - 14:23

List Question

What is the number of arrangements in the word "DAUGHTER" where vowels are never together?

Problem concerning the use of Pigeonhole (Box) principle

Prove the identity $ \sum\limits_{i=0}^{n} (-1)^{i} (a+2i) \binom{n}{i} \binom{a+n+i}{n+1}^{-1}=(n+1) \delta_{a,0}$

How to find the number of elements which share all the characteristics when there are many sets?

Counting the sets with elements satisfying $k_i\ge0$, $\sum_i k_i=K$, $\sum_i i k_i=N $.

A bijection between Motzkin paths and 3-colored signed Dyck path homomorphs

Looking for a challenging task or variant related to the knight's tour problem

Bitstrings of length n which the first three bits are not equal using complement

What does this count?

Let $L$ be a latin square whose entries are $L_{ij} = i+j (mod n)$. Then there are no $n$ distinct entries from unique rows and columns of $L$

A committee of 4 is to be formed out of 6 superheroes, 7 supervillains, and 4 citizens. How many ways to form a committee?

Evaluating a Difference Operator of a Product of Factorial Polynomials

Bitstrings of length n that do not contain the substring 10

How was the integral formula for the binomial coefficient discovered?

Number of ways to take parentheses

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