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  2. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    The greatest cube it is greater than is 3, so the first digit of the two-digit cube must be 3. Therefore, the cube root of 29791 is 31. Another example: Find the cube root of 456533. The cube root ends in 7. After the last three digits are taken away, 456 remains. 456 is greater than all the cubes up to 7 cubed. The first digit of the cube root ...

  3. Sums of three cubes - Wikipedia

    en.wikipedia.org/wiki/Sums_of_three_cubes

    Semi-log plot of solutions of + + = for integer , , and , and .Green bands denote values of proven not to have a solution.. In the mathematics of sums of powers, it is an open problem to characterize the numbers that can be expressed as a sum of three cubes of integers, allowing both positive and negative cubes in the sum.

  4. Highly composite number - Wikipedia

    en.wikipedia.org/wiki/Highly_composite_number

    It is false that all highly composite numbers are also Harshad numbers in base 10. The first highly composite number that is not a Harshad number is 245,044,800; it has a digit sum of 27, which does not divide evenly into 245,044,800. 10 of the first 38 highly composite numbers are superior highly composite numbers.

  5. Sum of two cubes - Wikipedia

    en.wikipedia.org/wiki/Sum_of_two_cubes

    A Cabtaxi number is the smallest positive number that can be expressed as a sum of two integer cubes in n ways, allowing the cubes to be negative or zero as well as positive. The smallest cabtaxi number after Cabtaxi(1) = 0, is Cabtaxi(2) = 91, [ 5 ] expressed as:

  6. Triangular number - Wikipedia

    en.wikipedia.org/wiki/Triangular_number

    A square whose side length is a triangular number can be partitioned into squares and half-squares whose areas add to cubes. This shows that the square of the n th triangular number is equal to the sum of the first n cube numbers. Also, the square of the n th triangular number is the same as the sum of the cubes of the integers 1 to n.

  7. List of sums of reciprocals - Wikipedia

    en.wikipedia.org/wiki/List_of_sums_of_reciprocals

    If the first term is a and the common ratio is r then the sum is ⁠ r / a (r − 1) ⁠. The Kempner series is the sum of the reciprocals of all positive integers not containing the digit "9" in base 10. Unlike the harmonic series, which does not exclude those numbers, this series converges, specifically to approximately 22.9207 .

  8. Fourth power - Wikipedia

    en.wikipedia.org/wiki/Fourth_power

    Fourth powers are also formed by multiplying a number by its cube. Furthermore, they are squares of squares. Some people refer to n 4 as n “ tesseracted ”, “ hypercubed ”, “ zenzizenzic ”, “ biquadrate ” or “ supercubed ” instead of “to the power of 4”.

  9. Proof by exhaustion - Wikipedia

    en.wikipedia.org/wiki/Proof_by_exhaustion

    Proof by exhaustion can be used to prove that if an integer is a perfect cube, then it must be either a multiple of 9, 1 more than a multiple of 9, or 1 less than a multiple of 9. [3] Proof: Each perfect cube is the cube of some integer n, where n is either a multiple of 3, 1 more than a multiple of 3, or 1 less than a multiple of 3. So these ...