wtf is this? how am i supposed to represent this using sigma notation?

https://en.m.wikipedia.org/wiki/Double_factorial
Now delete this stupid thread.

How about
[eqn]1 + \sum\limits_{n=1}^{\infty} \dfrac{\prod\limits_{m=0}^{n-1}2 \cdot m + 1}{n \cdot 3^n}[/eqn]

>>8459742
That summation equals ln(3/2) btw

>>8459762
thx

>>8459706
[eqn]
1 + \sum_{i=1}^{\infty} \frac{\pisum_{j=1}^{i}2j - 1}{i3^i}
[/eqn]

[eqn]\sum^{n}_{i=0}\frac{(2i+1)!}{2^n\cdot i! }[/eqn]

This is all you had to write brainlet.

I mean...
[eqn]\sum^{n}_{i=0}\frac{(2i+1)!}{2^n\cdot 5^n\cdot i! }[/eqn]

[eqn]\sum^{n}_{i=0}\frac{(2i+1)!}{2^i\cdot 5^i\cdot i! }[/eqn]

Or maybe this is the correct one. nvm im done with your dumb question op.

>>8459722
why does this even have a name it is literally just [eqn]\frac{(2n)!}{2^n\cdot n!}[/eqn]

>>8461239
So you don't have to write that bullshit every time you want to use it