All Questions
3
questions
13
votes
1
answer
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Notation: What is the scope of a sum?
I would interpret $\sum_{i=1}^2 x_i + y$ as $x_1 + x_2 + y$, but I would interpret $\sum_{i=1}^2 x_i + y_i$ as $x_1 + y_1 + x_2 + y_2$. I realize this is a little inconsistent. Should the latter be ...
- 233
3
votes
1
answer
150
views
Finite unordered sums
For all $n \geqslant 1,$ let $I_n = \{1, 2, \ldots, n\}.$
Let $X$ be a commutative semigroup.
Let $(x_i)_{i \in I_n}$ be a finite sequence in $X.$ That is to say,
let $x \colon I_n \to X$ be any ...
- 12.3k
4
votes
4
answers
654
views
Notation of symmetric sum notation
When you use the symmetric sum notation, for example, $$\sum_\text{sym}abc+a$$ if there are 3 variables, then does abc count once, 3 times or 6 times?
I am confused about repetitions of the same ...
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