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  2. Sylvester's sequence - Wikipedia

    en.wikipedia.org/wiki/Sylvester's_sequence

    The sequence can be used to prove that there are infinitely many prime numbers, as any prime can divide at most one number in the sequence. More strongly, no prime factor of a number in the sequence can be congruent to 5 modulo 6, and the sequence can be used to prove that there are infinitely many primes congruent to 7 modulo 12. [20]

  3. Geometric progression - Wikipedia

    en.wikipedia.org/wiki/Geometric_progression

    A geometric progression, also known as a geometric sequence, is a mathematical sequence of non-zero numbers where each term after the first is found by multiplying the previous one by a fixed number called the common ratio. For example, the sequence 2, 6, 18, 54, ... is a geometric progression with a common ratio of 3.

  4. Square pyramidal number - Wikipedia

    en.wikipedia.org/wiki/Square_pyramidal_number

    Formulas for summing consecutive squares to give a cubic polynomial, whose values are the square pyramidal numbers, are given by Archimedes, who used this sum as a lemma as part of a study of the volume of a cone, [2] and by Fibonacci, as part of a more general solution to the problem of finding formulas for sums of progressions of squares. [3]

  5. Geometric series - Wikipedia

    en.wikipedia.org/wiki/Geometric_series

    The geometric series is an infinite series derived from a special type of sequence called a geometric progression.This means that it is the sum of infinitely many terms of geometric progression: starting from the initial term , and the next one being the initial term multiplied by a constant number known as the common ratio .

  6. Sum of squares - Wikipedia

    en.wikipedia.org/wiki/Sum_of_squares

    Heron's formula for the area of a triangle can be re-written as using the sums of squares of a triangle's sides (and the sums of the squares of squares) The British flag theorem for rectangles equates two sums of two squares; The parallelogram law equates the sum of the squares of the four sides to the sum of the squares of the diagonals

  7. Congruum - Wikipedia

    en.wikipedia.org/wiki/Congruum

    The two right triangles with leg and hypotenuse (7,13) and (13,17) have equal third sides of length .The square of this side, 120, is a congruum: it is the difference between consecutive values in the arithmetic progression of squares 7 2, 13 2, 17 2.

  8. Pyramidal number - Wikipedia

    en.wikipedia.org/wiki/Pyramidal_number

    Geometric representation of the square pyramidal number 1 + 4 + 9 + 16 = 30. A pyramidal number is the number of points in a pyramid with a polygonal base and triangular sides. [1] The term often refers to square pyramidal numbers, which have a square base with four sides, but it can also refer to a pyramid with any number of sides. [2]

  9. Figurate number - Wikipedia

    en.wikipedia.org/wiki/Figurate_number

    To transform from the n-square (the square of size n) to the (n + 1)-square, one adjoins 2n + 1 elements: one to the end of each row (n elements), one to the end of each column (n elements), and a single one to the corner. For example, when transforming the 7-square to the 8-square, we add 15 elements; these adjunctions are the 8s in the above ...