Hot questions in Discrete Mathematics

51 votes
5 answers
121
38 votes
9 answers
123
How many $4$-digit even numbers have all $4$ digits distinct?$2240$$2296$$2620$$4536$
29 votes
6 answers
124
Indicate which of the following well-formed formulae are valid:$\left(P\Rightarrow Q\right) {\wedge} \left(Q \Rightarrow R\right) \Rightarrow \left(P \Rightarrow R\right)...
46 votes
6 answers
128
The minimum number of colours required to colour the vertices of a cycle with $n$ nodes in such a way that no two adjacent nodes have the same colour is$2$$3$$4$$n-2 \lef...
58 votes
9 answers
132
If the ordinary generating function of a sequence $\left \{a_n\right \}_{n=0}^\infty$ is $\large \frac{1+z}{(1-z)^3}$, then $a_3-a_0$ is equal to ___________ .
23 votes
2 answers
136