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  2. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    So, instead of proving that all positive integers eventually lead to 1, we can try to prove that 1 leads backwards to all positive integers. For any integer n, n ≡ 1 (mod 2) if and only if 3n + 1 ≡ 4 (mod 6). Equivalently, ⁠ n − 1 / 3 ⁠ ≡ 1 (mod 2) if and only if n ≡ 4 (mod 6).

  3. List of conjectures - Wikipedia

    en.wikipedia.org/wiki/List_of_conjectures

    Conjecture Field Comments Eponym(s) Cites 1/3–2/3 conjecture: order theory: n/a: 70 abc conjecture: number theory: ⇔Granville–Langevin conjecture, Vojta's conjecture in dimension 1 ⇒Erdős–Woods conjecture, Fermat–Catalan conjecture Formulated by David Masser and Joseph Oesterlé. [1] Proof claimed in 2012 by Shinichi Mochizuki: n/a ...

  4. 3x + 1 semigroup - Wikipedia

    en.wikipedia.org/wiki/3x_+_1_semigroup

    The elements of a generating set of this semigroup are related to the sequence of numbers involved in the still open Collatz conjecture or the "3x + 1 problem". The 3x + 1 semigroup has been used to prove a weaker form of the Collatz conjecture. In fact, it was in such context the concept of the 3x + 1 semigroup was introduced by H. Farkas in ...

  5. Erdős–Straus conjecture - Wikipedia

    en.wikipedia.org/wiki/Erdős–Straus_conjecture

    The conjecture is that, for every integer that is greater than or equal to 2, there exist positive integers , , and for which = + +. In other words, the number 4 / n {\displaystyle 4/n} can be written as a sum of three positive unit fractions .

  6. Dirichlet's theorem on arithmetic progressions - Wikipedia

    en.wikipedia.org/wiki/Dirichlet's_theorem_on...

    For example, 6n + 1 produces the same primes as 3n + 1, while 6n + 5 produces the same as 3n + 2 except for the only even prime 2. The following table lists several arithmetic progressions with infinitely many primes and the first few ones in each of them.

  7. List of unsolved problems in mathematics - Wikipedia

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

    Lander, Parkin, and Selfridge conjecture: if the sum of -th powers of positive integers is equal to a different sum of -th powers of positive integers, then +. Lemoine's conjecture : all odd integers greater than 5 {\displaystyle 5} can be represented as the sum of an odd prime number and an even semiprime .

  8. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    This is a list of notable integer sequences with links to their entries in the On-Line Encyclopedia of Integer Sequences. ... Positive integers n for which ...

  9. Goldbach's conjecture - Wikipedia

    en.wikipedia.org/wiki/Goldbach's_conjecture

    Goldbach's conjecture is one of the oldest and best-known unsolved problems in number theory and all of mathematics. It states that every even natural number greater than 2 is the sum of two prime numbers. The conjecture has been shown to hold for all integers less than 4 × 10 18 but remains unproven despite considerable effort.