How many words of length n with letters from {A,B,C} with atleast 1 occurence of AA?
66784
Number of strings lenght $n$ with no consecutive zeros
130513
LCM is associative: $\ \text{lcm}(\text{lcm}(a,b),c)=\text{lcm}(a,\text{lcm}(b,c))$
40848
$a\mid b,c\mid d\Rightarrow\,\gcd(a,c)\mid \gcd(b,d)$
65307
Simple combination/probability question based on string-length and possible-characters
152849
Expected Value of the number of letters we need to draw from the alphabet
129848
Counting the number of occurences of characters in a string
66294
Number of Derangements of the word BOTTLE
53639
Formula for number of 6 letter words from English alphabet if there is repetion and ordering
38809
In how many ways can the letters of word $PERMUTATIONS$ be arranged if there are always 4 letters between P and S?
79881
The Matching Problem/Derangements - n letters to n people
72853
What is the number of automorphisms (including identity) for permutation group $S_3$ on 3 letters?
87664
Combination of $n$ letter out of $3n$.
79702
Fraction whose items are words
9242
Should individual letters be preceded with "an"?
34334
Combinatorics Problem with symbols and spaces
158285
How to solve this combinatorial problem about selecting letters from different groups?
33633
Re:$ (a,b,c,d)=(pr+qs, qr-ps,pr-qs,ps+qr) $