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  2. Check digit - Wikipedia

    en.wikipedia.org/wiki/Check_digit

    For instance, the UPC-A barcode for a box of tissues is "036000241457". The last digit is the check digit "7", and if the other numbers are correct then the check digit calculation must produce 7. Add the odd number digits: 0+6+0+2+1+5 = 14. Multiply the result by 3: 14 × 3 = 42. Add the even number digits: 3+0+0+4+4 = 11.

  3. List of sums of reciprocals - Wikipedia

    en.wikipedia.org/wiki/List_of_sums_of_reciprocals

    The sum of the reciprocals of the Proth primes, of which there may be finitely many or infinitely many, is known to be finite, approximately 0.747392479. [2] The prime quadruplets are pairs of twin primes with only one odd number between them. The sum of the reciprocals of the numbers in prime quadruplets is approximately 0.8706.

  4. Proof without words - Wikipedia

    en.wikipedia.org/wiki/Proof_without_words

    Proof without words of the Nicomachus theorem (Gulley (2010)) that the sum of the first n cubes is the square of the n th triangular number. In mathematics, a proof without words (or visual proof) is an illustration of an identity or mathematical statement which can be demonstrated as self-evident by a diagram without any accompanying explanatory text.

  5. Spreadsheet - Wikipedia

    en.wikipedia.org/wiki/Spreadsheet

    Formulas in the B column multiply values from the A column using relative references, and the formula in B4 uses the SUM() function to find the sum of values in the B1:B3 range. A formula identifies the calculation needed to place the result in the cell it is contained within. A cell containing a formula, therefore, has two display components ...

  6. Ramanujan's sum - Wikipedia

    en.wikipedia.org/wiki/Ramanujan's_sum

    In number theory, Ramanujan's sum, usually denoted c q (n), is a function of two positive integer variables q and n defined by the formula c q ( n ) = ∑ 1 ≤ a ≤ q ( a , q ) = 1 e 2 π i a q n , {\displaystyle c_{q}(n)=\sum _{1\leq a\leq q \atop (a,q)=1}e^{2\pi i{\tfrac {a}{q}}n},}

  7. 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.

  8. Even and odd functions - Wikipedia

    en.wikipedia.org/wiki/Even_and_odd_functions

    The sum of two odd functions is odd. The difference between two odd functions is odd. The difference between two even functions is even. The sum of an even and odd function is not even or odd, unless one of the functions is equal to zero over the given domain.

  9. Squared triangular number - Wikipedia

    en.wikipedia.org/wiki/Squared_triangular_number

    The sum within each gmonon is a cube, so the sum of the whole table is a sum of cubes. [7] Visual demonstration that the square of a triangular number equals a sum of cubes. In the more recent mathematical literature, Edmonds (1957) provides a proof using summation by parts. [8]