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  2. Fermat number - Wikipedia

    en.wikipedia.org/wiki/Fermat_number

    That 641 is a factor of F 5 can be deduced from the equalities 641 = 2 7 × 5 + 1 and 641 = 2 4 + 5 4. It follows from the first equality that 2 7 × 5 ≡ −1 (mod 641) and therefore (raising to the fourth power) that 2 28 × 5 4 ≡ 1 (mod 641). On the other hand, the second equality implies that 5 4 ≡ −2 4 (mod 641

  3. Ackermann function - Wikipedia

    en.wikipedia.org/wiki/Ackermann_function

    For , however, it grows much more quickly; even (,) is about 2.00353 × 10 19 728, and the decimal expansion of (,) is very large by any typical measure, about 2.12004 × 10 6.03123 × 10 19 727. An interesting aspect is that the only arithmetic operation it ever uses is addition of 1.

  4. Formula for primes - Wikipedia

    en.wikipedia.org/wiki/Formula_for_primes

    Because the set of primes is a computably enumerable set, by Matiyasevich's theorem, it can be obtained from a system of Diophantine equations. Jones et al. (1976) found an explicit set of 14 Diophantine equations in 26 variables, such that a given number k + 2 is prime if and only if that system has a solution in nonnegative integers: [7]

  5. Catalan number - Wikipedia

    en.wikipedia.org/wiki/Catalan_number

    The only Catalan numbers C n that are odd are those for which n = 2 k − 1; all others are even. The only prime Catalan numbers are C 2 = 2 and C 3 = 5. [1] More generally, the multiplicity with which a prime p divides C n can be determined by first expressing n + 1 in base p. For p = 2, the multiplicity is the number

  6. Polynomial interpolation - Wikipedia

    en.wikipedia.org/wiki/Polynomial_interpolation

    The answer is unfortunately negative: Theorem — For any table of nodes there is a continuous function f ( x ) on an interval [ a , b ] for which the sequence of interpolating polynomials diverges on [ a , b ].

  7. Fibonacci sequence - Wikipedia

    en.wikipedia.org/wiki/Fibonacci_sequence

    For example, out of the 16 binary strings of length 4, there are F 5 = 5 without an odd number of consecutive 1 s—they are 0000, 0011, 0110, 1100, 1111. Equivalently, the number of subsets S of {1, ..., n } without an odd number of consecutive integers is F n +1 .

  8. Faulhaber's formula - Wikipedia

    en.wikipedia.org/wiki/Faulhaber's_formula

    Since a = n(n + 1)/2, these formulae show that for an odd power (greater than 1), the sum is a polynomial in n having factors n 2 and (n + 1) 2, while for an even power the polynomial has factors n, n + 1/2 and n + 1.

  9. Particular values of the Riemann zeta function - Wikipedia

    en.wikipedia.org/wiki/Particular_values_of_the...

    It is known that ζ(3) is irrational (Apéry's theorem) and that infinitely many of the numbers ζ(2n + 1) : n ∈ , are irrational. [1] There are also results on the irrationality of values of the Riemann zeta function at the elements of certain subsets of the positive odd integers; for example, at least one of ζ (5), ζ (7), ζ (9), or ζ ...