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  2. Ulam spiral - Wikipedia

    en.wikipedia.org/wiki/Ulam_spiral

    Ulam spiral of size 201×201. Black dots represent prime numbers. Diagonal, vertical, and horizontal lines with a high density of prime numbers are clearly visible. For comparison, a spiral with random odd numbers colored black (at the same density of primes in a 200x200 spiral).

  3. List of prime numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_prime_numbers

    All prime numbers from 31 to 6,469,693,189 for free download. Lists of Primes at the Prime Pages. The Nth Prime Page Nth prime through n=10^12, pi(x) through x=3*10^13, Random primes in same range. Interface to a list of the first 98 million primes (primes less than 2,000,000,000) Weisstein, Eric W. "Prime Number Sequences". MathWorld.

  4. Table of prime factors - Wikipedia

    en.wikipedia.org/wiki/Table_of_prime_factors

    An economical number has been defined as a frugal number, but also as a number that is either frugal or equidigital. gcd( m , n ) ( greatest common divisor of m and n ) is the product of all prime factors which are both in m and n (with the smallest multiplicity for m and n ).

  5. 200 (number) - Wikipedia

    en.wikipedia.org/wiki/200_(number)

    The number appears in the Padovan sequence, preceded by 86, 114, 151 (it is the sum of the first two of these). [1] The sum of Euler's totient function φ(x) over the first twenty-five integers is 200. 200 is the smallest base 10 unprimeable number – it cannot be turned into a prime number by changing just one of its digits to any other digit.

  6. Grid method multiplication - Wikipedia

    en.wikipedia.org/wiki/Grid_method_multiplication

    This is the "grid" or "boxes" structure which gives the multiplication method its name. Faced with a slightly larger multiplication, such as 34 × 13, pupils may initially be encouraged to also break this into tens. So, expanding 34 as 10 + 10 + 10 + 4 and 13 as 10 + 3, the product 34 × 13 might be represented:

  7. List of unsolved problems in mathematics - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Many mathematical problems have been stated but not yet solved. These problems come from many areas of mathematics, such as theoretical physics, computer science, algebra, analysis, combinatorics, algebraic, differential, discrete and Euclidean geometries, graph theory, group theory, model theory, number theory, set theory, Ramsey theory, dynamical systems, and partial differential equations.

  8. No-three-in-line problem - Wikipedia

    en.wikipedia.org/wiki/No-three-in-line_problem

    A set of 20 points in a 10 × 10 grid, with no three points in a line. The no-three-in-line problem in discrete geometry asks how many points can be placed in the n × n {\displaystyle n\times n} grid so that no three points lie on the same line.

  9. Happy number - Wikipedia

    en.wikipedia.org/wiki/Happy_number

    The palindromic prime 10 150006 + 7 426 247 × 10 75 000 + 1 is a 10-happy prime with 150 007 digits because the many 0s do not contribute to the sum of squared digits, and 1 2 + 7 2 + 4 2 + 2 2 + 6 2 + 2 2 + 4 2 + 7 2 + 1 2 = 176, which is a 10-happy number. Paul Jobling discovered the prime in 2005.