Generalization of the Gamma Function
By setting a=-1 and n: (n-1) you get the gamma function in the family of functions the final equation generates.
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2.3
The topic isn't well introduced nor motivated.
It would have been better with an introduction at the beginning of the video that explains the topic that is going to be discussed (not just "today we'll be integrating this function"), and gives motivation for why the viewer should be interested in the topic.
For example, what are the properties of the function that is being integrated? And what is the importance of the integral?
The fact that this is a generalisation of the Gamma function is mentioned in the title and description, but this fact is not addressed in the video.
Moreover I believe this topic is more useful to students looking for proofs of certain results, rather than for a general audience.
This is more of a small technical result, while the scope of SoME is more towards explaining "wider" results, or niche topics that spark interest.
In any case, the author provides a detailed derivation of the result, and gives quite clear explanations for each step.
The only step which I think should have been commented better is at 1:51 where the "induction" step happens and the integral is turned into a sum: the way it is written in the video doesn't make it clear that it is a finite sum, and the author should have clarified that the iteration of integration by parts only needs to be applied n times because at the n-th step the term becomes zero.
Also, the notation used from 3:09 is quite cumbersome to understand: the summation symbol is used, but part of the sum is written expanded out, in a way that makes it look like it is inside the summation multiplying the other terms. Perhaps it was a mistake, but if it were intentional it should have been clarified.
Also, I think that the steps to write the sum in summation notation are quite trivial and should not have been given so much importance in the derivation.