7.27.1 Top new questions this week

7.27.1.1 How to make figures in a casual, old-fashioned style

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=253037

I'm writing a math textbook and use Mathematica to make figures. However, like all modern software, Mathematica produces perfectly crisp mathematically accurate figures. Meanwhile, I feel that old-... 
[plotting] [graphics] [style]
 

asked by Wynne https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36616 13 votes

answered by flinty https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72682 13 votes

7.27.1.2 Solve equation with summation and factorial over Integers

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=252995

Find all $\{ m, n \} \in \mathbb{Z}^+$ such that 
$$\sum\limits_{k=1}^m k! = n^2 .$$ 
The two solutions are $\{ m,n \} = \{ 1,1 \}$ and $\{ 3,3 \}$, as can be confirmed.  Here is how to solve this ... 
[equation-solving] [findinstance]
 

asked by David G. Stork https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9735 8 votes

answered by yarchik https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9469 2 votes

7.27.1.3 Invisible _ in documentation with Mathematica 12.3.1?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=253114

I'm using Mathematica 12.3.1 on Windows. 
Most or not all pages do not show the Underscore character with Patterns. 
Is this only on my laptop? 
e.g. Documentation ref/DirectedEdge 
 
or ref/Cases 
 
When I ... 
[front-end] [notebooks]
 

asked by Lou https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=150 7 votes

answered by Rob F https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=45578 7 votes

7.27.1.4 Plot3D + WhenEvent + NDSolve

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=253092

Given: 
$\begin{cases} \dot{x}=-x-By^2 \\ \dot{y}=Ax-y^3 \end{cases}$ 
where $x,y$ - variables; 
$A=[2;4],B=[0.2;2]$ - positive parameters; 
My task is to find the time $t_n$ of the first intersection of ... 
[differential-equations] [dynamic] [nonlinear] [event-detection]
 

asked by dtn https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=67019 6 votes

answered by Ulrich Neumann https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=53677 8 votes

7.27.1.5 How to find all possible paths between a collection of vertices in a DAG graph

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=252947

I have a toy example "system" that is a DAG and has 16 vertices. 
Suppose I have a collection of vertices "collection". 
How can I find all paths that passes through at least all ... 
[graphs-and-networks]
 

asked by Lou https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=150 6 votes

answered by creidhne https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=41569 3 votes

7.27.1.6 Learning curve for Mathematica

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=253209

May be some of you (moderators and custodians) would discard this question as opinion-based and requiring discussion, but I didn't want the effort to go to waste so felt compelled to ask. Please feel ... 
[legending]
 

asked by Syed https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=81355 5 votes

answered by David G. Stork https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9735 5 votes

7.27.1.7 Prove a relation involving Floor holds for arbitrary $n$

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=253117

The 1968 International Mathematical Olympiad asks contestants to prove this relation involving the floor function for all $n \in \mathbb{N}$: 
$$\left\lfloor \frac{n + 2^0}{2^1} \right\rfloor + \left\... 
[forall] [floor]
 

asked by David G. Stork https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9735 5 votes