I saw a different pattern again
8,16,20,.....
I saw 16 as 3*4+4 (I added the corner blocks seperately)
I saw 20 as 5*4+4 (again I added the corner blocks afterwards.)
Looking at the patter I would get 8=1*4+4 that's true, great,
so I have
n 1 2 3
number of squares 1*4+4, 3*4+4, 5*4+4, ......
now lets look at a pattern for 1,3,5 etc ... they are getting bigger by 2s .... mmm, (2n-1)
So
$$\\T_n=(2n-1)*4+4\\
T_n=4(2n-1)+4\\
T_n=4[(2n-1)+1]\\
T_n=4[2n]\\
T_n=8n\\$$
so
$$T_{100}=8*100=800 squares$$
Yet another proof that
ALL ROADS LEAD TO ROME. (๑‵●‿●‵๑)
This is a good question.
$$\displaystyle\lim_{n\rightarrow\infty}\left(1+\frac{1}{n}\right)^n=2.718281828.....\qquad=e\\$$
This limit is used all the time (for continual compounding) so it was decided to give this number a formal symbol, that symbol is e
e is called Euler's number after the Swiss mathematician Euler, it is also called the Napier constant.
Here is the graph to show you
https://www.desmos.com/calculator/fa8qrqn33u
To derive e requires higher mathematics but here are some related web pages. ヽ(^o^)ノ