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  2. Product (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Product_(mathematics)

    The product operator for the product of a sequence is denoted by the capital Greek letter pi Π (in analogy to the use of the capital Sigma Σ as summation symbol). [1] For example, the expression ∏ i = 1 6 i 2 {\displaystyle \textstyle \prod _{i=1}^{6}i^{2}} is another way of writing ⁠ 1 ⋅ 4 ⋅ 9 ⋅ 16 ⋅ 25 ⋅ 36 {\displaystyle 1 ...

  3. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total.Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  4. Abel's summation formula - Wikipedia

    en.wikipedia.org/wiki/Abel's_summation_formula

    Abel's summation formula can be generalized to the case where is only assumed to be continuous if the integral is interpreted as a Riemann–Stieltjes integral: ∑ x < n ≤ y a n ϕ ( n ) = A ( y ) ϕ ( y ) − A ( x ) ϕ ( x ) − ∫ x y A ( u ) d ϕ ( u ) . {\displaystyle \sum _{x<n\leq y}a_{n}\phi (n)=A(y)\phi (y)-A(x)\phi (x)-\int _{x ...

  5. Summation by parts - Wikipedia

    en.wikipedia.org/wiki/Summation_by_parts

    In mathematics, summation by parts transforms the summation of products of sequences into other summations, often simplifying the computation or (especially) estimation of certain types of sums. It is also called Abel's lemma or Abel transformation , named after Niels Henrik Abel who introduced it in 1826.

  6. Direct product - Wikipedia

    en.wikipedia.org/wiki/Direct_product

    The direct sum and direct product are not isomorphic for infinite indices, where the elements of a direct sum are zero for all but for a finite number of entries. They are dual in the sense of category theory : the direct sum is the coproduct , while the direct product is the product.

  7. Series (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Series_(mathematics)

    A series or, redundantly, an infinite series, is an infinite sum.It is often represented as [8] [15] [16] + + + + + +, where the terms are the members of a sequence of numbers, functions, or anything else that can be added.

  8. Kahan summation algorithm - Wikipedia

    en.wikipedia.org/wiki/Kahan_summation_algorithm

    The algorithm performs summation with two accumulators: sum holds the sum, and c accumulates the parts not assimilated into sum, to nudge the low-order part of sum the next time around. Thus the summation proceeds with "guard digits" in c , which is better than not having any, but is not as good as performing the calculations with double the ...

  9. Sum-product number - Wikipedia

    en.wikipedia.org/wiki/Sum-product_number

    The natural numbers 0 and 1 are trivial sum-product numbers for all , and all other sum-product numbers are nontrivial sum-product numbers. For example, the number 144 in base 10 is a sum-product number, because 1 + 4 + 4 = 9 {\displaystyle 1+4+4=9} , 1 × 4 × 4 = 16 {\displaystyle 1\times 4\times 4=16} , and 9 × 16 = 144 {\displaystyle 9 ...