Any nonnegative integer \$m\$, for arbitrary natural \$r\$, can be written as a unique series of \$r\$ combinations such that $$m=\sum\limits_{i=1}^{r}\begin{pmatrix}C_i\\i\end{pmatrix}$$ provided the sequence \$C\$ both strictly increases (i.e. \$C_{\ell-1}\lneq C_\ell\$) and consists solely of ...

The existing factorial challenge has some restrictions on the domain, performance, and banning built-ins. I opened a meta question about it a week ago, and as per the meta consensus, we decided to post a new vanilla factorial challenge. The sandboxed challenge is here. Now the problem is: Should ...

Is my triangle on the lattice? decision-problem code-golf geometry Write a program or function which takes three positive integers \$a^2, b^2, c^2\$ and returns/outputs one value if there is, and a different value if there isn't, a triangle on the square lattice, whose sides' lengths are \$a, b, ...

Let's just see how this goes If you've ever listened to the radio program "I'm sorry, I haven't a clue", then you've probably heard of the game called "Mornington Crescent". For those who haven't, it's a game where players name random stations on the London Underground network. The first person t...

Substandard deviation The mean of a sample \$(x_1,\dots,x_n)\$ is defined as \$\bar x=\frac1n\sum_{i=1}^n x_i\$. The (uncorrected) standard deviation of the sample is defined as \$\sqrt{\frac1n\sum (x_i-\bar x)^2}\$. It measures how dispersed the sample is: a large standard deviation indicates th...

Write the shortest program that prints the sound my alarm clock makes, and stops after an inputted number of beeps. For reference, here is the sound my alarm makes: beep beep beep beep beep beepbeep beepbeep beepbeep beepbeep beepbeep beepbeepbeep beepbeepbeep beepbeepbeep beepbeepbeep beepbeepbe...

How Many Notches Are On Texas Red's Pistol? The song, Big Iron, by Marty Robbins, is about an Arizona Ranger who rode into the town of Agua Fria to take the outlaw Texas Red alive (or maybe dead), armed with only the Big Iron (a .45 revolver) on his hip. Texas Red, despite being only 24 years old...

Feedback Wanted Is this too vague? should I change it to something like "create a quine with the fewest unique bytes", or perhaps adapt another existing challenge that might otherwise use lots of repeated bytes? Maybe the idea is just too boring on its own and I should create a new proper challe...

Note This is the decryption challenge. The encryption challenge can be found here. Challenge The challenge is to decrypt a given string, using the rules as specified below. The string will only contain lowercase alphabets, digits, and/or blank spaces. If you want to know how the input string has ...