Yea that’s not explained better than a math teach. They just swapped notation common in math, for notation common in one specific programming language. it’s only easier for the audience who happens to be familiar with programming in general, and that language in particular.
one specific programming language
I think you’d be hard pressed to find someone with any sort of programming background, even just as a hobbyist, who doesn’t understand that for loop notation, whether or not they know the specific language it’s from. (I couldn’t even tell you what specific language that’s from, because that notation matches so many different ones.)
I have a 15 year old son; he definitely has not seen summation in math classes yet, but he has far more than enough programming experience (even just from school) to understand the for loop.
Java/C# would have types before the variables:
double sum = 0d;
for (int i = 0; i < 4; i++)
sum += 3 * i;
