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  2. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    Equivalently, ⁠ 2n − 1 / 3 ⁠ ≡ 1 (mod 2) if and only if n2 (mod 3). Conjecturally, this inverse relation forms a tree except for a 12 loop (the inverse of the 12 loop of the function f(n) revised as indicated above). Alternatively, replace the 3n + 1 with ⁠ n ′ / H(n ′) ⁠ where n ′ = 3n + 1 and H(n ′) is the ...

  3. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    φ(n) is the number of positive integers not greater than n that are coprime with n. A000010: Lucas numbers L(n) 2, 1, 3, 4, 7, 11, 18, 29, 47, 76, ... L(n) = L(n1) + L(n2) for n2, with L(0) = 2 and L(1) = 1. A000032: Prime numbers p n: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ... The prime numbers p n, with n1. A prime number is ...

  4. Goldbach's conjecture - Wikipedia

    en.wikipedia.org/wiki/Goldbach's_conjecture

    Thus if n is a large even integer and m is a number between 3 and ⁠ n / 2 ⁠, then one might expect the probability of m and n − m simultaneously being prime to be ⁠ 1 / ln m ln(n − m) ⁠. If one pursues this heuristic, one might expect the total number of ways to write a large even integer n as the sum of two odd primes to be roughly

  5. Parity of zero - Wikipedia

    en.wikipedia.org/wiki/Parity_of_zero

    Half of the numbers in a given range end in 0, 2, 4, 6, 8 and the other half in 1, 3, 5, 7, 9, so it makes sense to include 0 with the other even numbers. However, in 1977, a Paris rationing system led to confusion: on an odd-only day, the police avoided fining drivers whose plates ended in 0, because they did not know whether 0 was even. [ 67 ]

  6. Python syntax and semantics - Wikipedia

    en.wikipedia.org/wiki/Python_syntax_and_semantics

    Numeric literals in Python are of the normal sort, e.g. 0, -1, 3.4, 3.5e-8. Python has arbitrary-length integers and automatically increases their storage size as necessary. Prior to Python 3, there were two kinds of integral numbers: traditional fixed size integers and "long" integers of arbitrary size.

  7. Parity (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Parity_(mathematics)

    That is, if the last digit is 1, 3, 5, 7, or 9, then it is odd; otherwise it is even—as the last digit of any even number is 0, 2, 4, 6, or 8. The same idea will work using any even base. In particular, a number expressed in the binary numeral system is odd if its last digit is 1; and it is even if its last digit is 0. In an odd base, the ...

  8. Fibonacci sequence - Wikipedia

    en.wikipedia.org/wiki/Fibonacci_sequence

    A bijection with the sums to n is to replace 1 with 0 and 2 with 11. The number of binary strings of length n without an even number of consecutive 0 s or 1 s is 2F n. For example, out of the 16 binary strings of length 4, there are 2F 4 = 6 without an even number of consecutive 0 s or 1 s—they are 0001, 0111, 0101, 1000, 1010, 1110. There is ...

  9. Singly and doubly even - Wikipedia

    en.wikipedia.org/wiki/Singly_and_doubly_even

    The 2-order of n is written ν 2 (n) or ord 2 (n). It is not to be confused with the multiplicative order modulo 2. The 2-order provides a unified description of various classes of integers defined by evenness: Odd numbers are those with ν 2 (n) = 0, i.e., integers of the form 2m + 1. Even numbers are those with ν 2 (n) > 0, i.e., integers of ...