# Langford problem

## Series: Linear Optimization

# Who Betrayed Dune’s Duke Leto?

## Series: Riddler Puzzles

# Flowfree

## Series: Linear Optimization

# Riddle of the pilgrims

## Series: Linear Optimization

# Unusual Crossword

# Problems for children from 5 to 15 by V.I. Arnold

# A curious identity involving $e$ and $\pi$

## Series: Infinite Series

# Problems by Ramanujan

# Problems in summation of series

## Series: Infinite Series

&= \int \frac{1}{1-z}dz = -ln(1-z) \

\implies f(z) &= -\frac{ln(1-z)}{1-z} \end{align*} $$ Problem 2 Evaluate $\sum_{n=0}^{\infty} \frac{(-1)^n)}{3^n(2n + 1)}$.