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  2. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    For example, for 2 5 a + 1 there are 3 increases as 1 iterates to 2, 1, 2, 1, and finally to 2 so the result is 3 3 a + 2; for 2 2 a + 1 there is only 1 increase as 1 rises to 2 and falls to 1 so the result is 3a + 1. When b is 2 k − 1 then there will be k rises and the result will be 3 k a + 3 k − 1.

  3. Divisibility rule - Wikipedia

    en.wikipedia.org/wiki/Divisibility_rule

    Subtracting 2 times the last digit from the rest gives a multiple of 3. (Works because 21 is divisible by 3) 405: 40 - 5 x 2 = 40 - 10 = 30 = 3 x 10 4: The last two digits form a number that is divisible by 4. [2] [3] 40,832: 32 is divisible by 4. If the tens digit is even, the ones digit must be 0, 4, or 8.

  4. Primality test - Wikipedia

    en.wikipedia.org/wiki/Primality_test

    There are only 21853 pseudoprimes base 2 that are less than 2.5 × 10 10 (see page 1005 of [3]). This means that, for n up to 2.5 × 10 10, if 2 n −1 (modulo n) equals 1, then n is prime, unless n is one of these 21853 pseudoprimes. Some composite numbers (Carmichael numbers) have the property that a n − 1 is 1 (modulo n) for every a that ...

  5. Lipinski's rule of five - Wikipedia

    en.wikipedia.org/wiki/Lipinski's_Rule_of_Five

    [2] [4] Omeprazole is a popular drug that conforms to Lipinski's rule of five. Some authors have criticized the rule of five for the implicit assumption that passive diffusion is the only important mechanism for the entry of drugs into cells, ignoring the role of transporters. For example, O'Hagan and co-authors wrote as follows: [5]

  6. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...

  7. Degree of a polynomial - Wikipedia

    en.wikipedia.org/wiki/Degree_of_a_polynomial

    The degree of the sum (or difference) of two polynomials is less than or equal to the greater of their degrees; that is, and . For example, the degree of is 2, and 2 ≤ max {3, 3}. The equality always holds when the degrees of the polynomials are different. For example, the degree of is 3, and 3 = max {3, 2}.

  8. Table of prime factors - Wikipedia

    en.wikipedia.org/wiki/Table_of_prime_factors

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  9. Scientific notation - Wikipedia

    en.wikipedia.org/wiki/Scientific_notation

    Any real number can be written in the form m × 10 ^ n in many ways: for example, 350 can be written as 3.5 × 10 2 or 35 × 10 1 or 350 × 10 0. In normalized scientific notation (called "standard form" in the United Kingdom), the exponent n is chosen so that the absolute value of m remains at least one but less than ten ( 1 ≤ | m | < 10 ).