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  2. Euler numbers - Wikipedia

    en.wikipedia.org/wiki/Euler_numbers

    The Euler numbers appear in the Taylor series expansions of the secant and hyperbolic secant functions. The latter is the function in the definition. The latter is the function in the definition. They also occur in combinatorics , specifically when counting the number of alternating permutations of a set with an even number of elements.

  3. e (mathematical constant) - Wikipedia

    en.wikipedia.org/wiki/E_(mathematical_constant)

    The number e is a mathematical constant approximately equal to 2.71828 that is the base of the natural logarithm and exponential function.It is sometimes called Euler's number, after the Swiss mathematician Leonhard Euler, though this can invite confusion with Euler numbers, or with Euler's constant, a different constant typically denoted .

  4. Eulerian number - Wikipedia

    en.wikipedia.org/wiki/Eulerian_number

    In combinatorics, the Eulerian number (,) is the number of permutations of the numbers 1 to in which exactly elements are greater than the previous element (permutations with "ascents"). Leonhard Euler investigated them and associated polynomials in his 1755 book Institutiones calculi differentialis .

  5. Euler characteristic - Wikipedia

    en.wikipedia.org/wiki/Euler_characteristic

    For every combinatorial cell complex, one defines the Euler characteristic as the number of 0-cells, minus the number of 1-cells, plus the number of 2-cells, etc., if this alternating sum is finite. In particular, the Euler characteristic of a finite set is simply its cardinality, and the Euler characteristic of a graph is the number of ...

  6. List of topics named after Leonhard Euler - Wikipedia

    en.wikipedia.org/wiki/Euler's_numbers

    Euler's number, e = 2.71828 . . . , the base of the natural logarithm; Euler's idoneal numbers, a set of 65 or possibly 66 or 67 integers with special properties; Euler numbers, integers occurring in the coefficients of the Taylor series of 1/cosh t; Eulerian numbers count certain types of permutations.

  7. Euler's constant - Wikipedia

    en.wikipedia.org/wiki/Euler's_constant

    Using the same approach, in 2013, M. Ram Murty and A. Zaytseva showed that the generalized Euler constants have the same property, [3] [44] [45] where the generalized Euler constant are defined as = (= ⁡ = ()), where ⁠ ⁠ is a fixed list of prime numbers, () = if at least one of the primes in ⁠ ⁠ is a prime factor of ⁠ ⁠, and ...

  8. Leonhard Euler - Wikipedia

    en.wikipedia.org/wiki/Leonhard_Euler

    Euler describes 18 such genres, with the general definition 2 m A, where A is the "exponent" of the genre (i.e. the sum of the exponents of 3 and 5) and 2 m (where "m is an indefinite number, small or large, so long as the sounds are perceptible" [114]), expresses that the relation holds independently of the number of octaves concerned.

  9. Euler's totient function - Wikipedia

    en.wikipedia.org/wiki/Euler's_totient_function

    Euler's totient function is a multiplicative function, meaning that if two numbers m and n are relatively prime, then φ(mn) = φ(m)φ(n). [ 4 ] [ 5 ] This function gives the order of the multiplicative group of integers modulo n (the group of units of the ring Z / n Z {\displaystyle \mathbb {Z} /n\mathbb {Z} } ). [ 6 ]