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Apr
12
accepted Prove that $(A,B)\sim(P,Q)$ and $(C,D)\sim (P,Q)\implies (A,B)\sim (C,D)$?
Apr
6
accepted Equations of the tangent lines of $y=x^4$ at the point $(2,0)$?
Apr
2
accepted How to show that $\frac{-1}{x^2}=0$ has no solutions?
Apr
2
accepted Are there two meanings to induction?
Feb
16
accepted $4$ judges must distribute grades from $1$ to $6$ for each participant. In how many ways one can score $22$ points?
Feb
9
accepted How to obtain the chromatic polynomial of $C_5$?
Feb
9
accepted What is the connection with $g=1+\frac{1}{g}$ and $G_n= 1+\frac{1}{G_{n-1}}$?
Feb
8
accepted Find the number of ways to obtain a total of $15$ points by throwing $4$ different dice?
Feb
7
accepted What is the need of exponential generating functions on combinatorial problems?
Feb
1
accepted What is $\langle I\rangle$ in this text?
Jan
28
accepted Confusion about Hajós construction?
Jan
27
accepted What is this binding function?
Jan
13
accepted Why the sequence generated by $x+e^x$ is $(1,x,\frac{x^2}{2!},\frac{x^3}{3!},\frac{x^4}{4!}\ldots)$?
Jan
7
accepted Why is it important to have the closed form of a generating function?
Jan
7
accepted Why the generating function of $a_r=r$ is $xf'(x)$ instead of $f'(x)$?
Jan
7
accepted How $(r-k){r \choose r-k}$ becomes $r{r-1 \choose r-k-1}$?
Jan
6
accepted Differentiating $1/(1-x)$ using the fact that $[x^n]'=nx^{n-1}$?
Jan
3
accepted Is there only one continuous-everywhere non-differentiable funtion?
Jan
2
accepted What's umbral calculus about?
Dec
31
accepted Does the maximum cut implies the minimum flow?