Summation notation

Writes the sum of a finite list of numbers a_1 through a_n compactly using the capital sigma symbol. It is used whenever a long or general sequence of terms is added up.

i = 1 \sum n a_{i} = a_{1} + a_{2} + \dots + a_{n}

\sum_{i=1}^{n} a_i = a_1 + a_2 + \cdots + a_n

What the symbols mean

$i$	index of summation, running from 1 to n
$n$	upper limit of the index, the number of terms
$a_{i}$	the i-th term of the sequence

About this formula

FieldMathematics
TopicSequences and series
LevelHigh school
Also calledsum of a sequence, sigma notation, summation, sum of terms, finite sum, sigma sum
SourceWikidata Q218005

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What the symbols mean

About this formula

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