The Busy Beaver value S ( n ) is the maximum number of steps that an n-state 2-symbol Turing machine can perform from the all-zero tape before halting. S was historically introduced by Tibor Radó in 1962 as one of the simplest examples of an uncomputable function. We prove that S (5) = 47,176,870 using the Coq proof assistant. The proof enumerates 181,385,789 Turing machines with 5 states and, for each machine, decides whether it halts or not. Our result marks the first determination of a new Busy Beaver value in over 40 years and the first Busy Beaver value ever to be formally verified, attesting to the effectiveness of massively collaborative online research (bbchallenge.org).

We introduce $\textit{scadnano}$ (https://scadnano.org) (short for "scriptable cadnano"), a computational tool for designing synthetic DNA structures. Its design is based heavily on cadnano, the most widely-used software for designing DNA origami, with three main differences: 1. scadnano runs entirely in the browser, with $\textit{no software installation}$ required. 2. scadnano designs, while they can be edited manually, can also be created and edited by a $\textit{well-documented Python scripting library}$, to help automate tedious tasks. 3. The scadnano file format is $\textit{easily human-readable}$. This goal is closely aligned with the scripting library, intended to be helpful when debugging scripts or interfacing with other software. The format is also somewhat more expressive than that of cadnano, able to describe a broader range of DNA structures than just DNA origami.