10.6.1 Top new questions this week

10.6.1.1 Early computer art - reproducing Georg Nees "Schotter" and "K27"
10.6.1.2 How to match a pattern only when it is not used as a head?
10.6.1.3 What's the difference between With and ReplaceAll?
10.6.1.4 Why can't I use logic operator Or to specify multiple events with WhenEvent?
10.6.1.5 Ordering with repeats
10.6.1.6 How to "factor out" units?
10.6.1.7 Getting formulas like $E[\operatorname Tr (A^3 (A^T)^3]=n^4+10n^2+4n$
10.6.1.1 Early computer art - reproducing Georg Nees "Schotter" and "K27"

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298265

Georg Nees (1926 - 2016) was a pioneer of computer art. He studied mathematics, physics and philosophy in Erlangen and Stuttgart. In 1977, he was appointed Professor of Applied computer science at the ... 
[plotting] [graphics] [generative-art]
 
asked by eldo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14254 Score of 21
answered by Daniel Huber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46318 Score of 14
10.6.1.2 How to match a pattern only when it is not used as a head?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298374

I am working on modifying a mathematical expression and need some assistance. I have the following equation: 
 -27 f + 27 f[1 + n] - 9 f[2 + n] + f[3 + n] == 1 + 3 n 
 
... 
[pattern-matching]
 
asked by faceclean https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=52526 Score of 11
answered by eldo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14254 Score of 7
10.6.1.3 What's the difference between With and ReplaceAll?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298319

A wolfram Tutorial mentions that  ReplaceAll  and  With  are similar: 
 
The way ... 
[replacement] [pattern-matching] [core-language] [scoping]
 
asked by ions me https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=62529 Score of 9
answered by Sjoerd Smit https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=43522 Score of 11
10.6.1.4 Why can't I use logic operator Or to specify multiple events with WhenEvent?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298307

I want to use logic operator  Or  to specify multiple events. 
After reading these very helpful posts here and here, it seems to be better to use a function to inlude ... 
[differential-equations] [event-detection]
 
asked by xinxin guo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4756 Score of 8
answered by xzczd https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1871 Score of 7
10.6.1.5 Ordering with repeats

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298186

A quick question on list ordering, how can I easily get the ordering of the list, so that, for 
 {0, Sqrt[3], 2 Sqrt[3], Sqrt[3], 3, 2 Sqrt[3]} 
 
I get 
... 
[list-manipulation] [sorting] [order]
 
asked by sam wolfe https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=64001 Score of 8
answered by eldo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14254 Score of 6
10.6.1.6 How to "factor out" units?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298418

I have a huge expression that makes use of Mathematica's units support ( Quantity[] ) that I know evaluates to a dimensionless quantity. However, I'm unable to get <... 
[simplifying-expressions] [units]
 
asked by  https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=96738 Score of 7
answered by creidhne https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=41569 Score of 6
10.6.1.7 Getting formulas like $E[\operatorname Tr (A^3 (A^T)^3]=n^4+10n^2+4n$

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=298260

Suppose $A$ is an random $n\times n$ matrix with standard normal entries. 
A user was able to obtain the following formula by enumerating all diagrams by hand: 
$$E[\operatorname{Tr}(A^3 (A^T)^3]=n^4+... 
[probability-or-statistics] [algebraic-manipulation]
 
asked by Yaroslav Bulatov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=217 Score of 7
answered by Bob Hanlon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9362 Score of 8