# Tagged Questions

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### Closed Form CDF of the Variance Gamma Distribution

What is the closed form cumulative distribution function of the variance gamma distribution? The PDF is ...
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### Is there a closed form for $\sum_{i=0}^{\text{min}(k,t)} {{\binom k i} \over {\binom t i}}\cdot x^i$?

Is there a closed form for the following summation? ($k,t \in N, x\in \mathbb R^+$) $$f(x,k,t)=\sum_{i=0}^{\text{min}(k,t)} {{\binom k i} \over {\binom t i}}\cdot x^i$$
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### Closed Form Cantor Snake Function

Does anyone have the closed form for the Cantor-Snake function and its inverse? By Cantor-Snake, I mean the bijection that maps the Naturals to the Rations - the classic proof that the rationals ...
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### Formulating math problem with rounding / discrete step

I have this problem, that can easily be solved by simulation or numerical optimization, but I wonder how to write it as a mathematical problem? It's two pricing schemes, one cost is evaluated at ...
### Addition formula for $f_n(x+y)$ in closed form.
$n$ is a positive integer. $$f_n(x)^n+\left(\frac{df_n(x)}{dx}\right)^n=1$$ $f_n(0)=0$, $f_n'(0)=1$ then I am looking for the addition formula for $f_n(x+y)$ in closed form. if $n=1$ then ...