Counting Operations

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Good Evening,

Context:

I wanted to count the operations for calculate the coefficents in the newton base if you have $n+1$ datas.

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$$f_j=p_j(x_j)=a_0+\sum_{i=1}^j(a_i\prod_{k=0}^{{i-1}}(x_j-x_k))\ \ \ j,i=1,..,n$$

maybe you can help me to understand the counting in my script, because I have another solution. I want to count how many operations I need to calculate this:

$$a_j=\frac{f_j-a_0-\sum_{i=1}^{j-1}(a_i\prod_{k=0}^{i-1}(x_j-x_k)}{\prod_{k=0}^{j-1}(x_j-x_k)}$$

I would say, we have in the deonominator $j$ subtractions and $j-1$ multiplications. In the numerator we have $1+2+...+(j-1)$ Subtractions and also $1+2+...+(j-1)$ multiplications and then $j$ subtractions and in the end one Divsion.

Thats what I found in my script, but does not the 1 subtraction $-a_0$ is missing?

Thanks for helping me!:)