cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

A070888 Numerator of Sum_{k=1..n} mu(k)/k.

Original entry on oeis.org

1, 1, 1, 1, -1, 2, -1, -1, -1, 19, -1, -1, -2323, -89, 304, 304, 163, 163, -81988, -81988, -15019, 410857, -249979, -249979, -249979, 4165258, 4165258, 4165258, 9246047, -65721449, -4193929329, -4193929329, -6504197377, -302679716, 2562470143
Offset: 1

Views

Author

Donald S. McDonald, May 17 2002

Keywords

Comments

Sum_{k>0} mu(k)/k = limit_{n->oo} A070888(n)/A070889(n) = 0. - Jean-François Alcover, Apr 18 2013. This is equivalent to the Prime Number Theorem! - N. J. A. Sloane, Feb 04 2022

Examples

			a(6) = 2 because 1-1/2-1/3-1/5+1/6 = 4/30 = 2/15.
		

References

  • Harold M. Edwards, Riemann's Zeta Function, Dover Publications, New York, 1974 (ISBN 978-0-486-41740-0), p. 92.
  • Edmund Landau, Handbuch der Lehre von der Verteilung der Primzahlen, Chelsea Publishing, NY 1953, p. 568.

Crossrefs

Cf. A008683, A068337, A070889 (denominators).

Programs

  • Maple
    T:= 0:
    for n from 1 to 100 do
      T:= T + numtheory:-mobius(n)/n;
      A[n]:= numer(T)
    od:
    seq(A[n],n=1..100); # Robert Israel, Aug 04 2014
  • Mathematica
    Table[ Numerator[ Sum[ MoebiusMu[k]/k, {k, 1, n}]], {n, 1, 37}]
  • PARI
    t = 0; v = []; for( n = 1, 60, t= t + moebius( n) / n; v = concat( v, numerator( t))); v \\ adapted to latest PARI version by Michel Marcus, Aug 04 2014
    
  • Python
    from functools import lru_cache
    from sympy import harmonic
    @lru_cache(maxsize=None)
    def f(n):
        if n <= 1:
            return 1
        c, j = 1, 2
        k1 = n//j
        while k1 > 1:
            j2 = n//k1 + 1
            c += (harmonic(j-1)-harmonic(j2-1))*f(k1)
            j, k1 = j2, n//j2
        return c+harmonic(j-1)-harmonic(n)
    def A070888(n): return f(n).numerator # Chai Wah Wu, Nov 03 2023

Extensions

Edited by Robert G. Wilson v, Jun 10 2002

A070891 Denominator of Sum_{k=1..n} mu(k)/k when it changes sign.

Original entry on oeis.org

30, 15, 105, 210, 2310, 5005, 1616615, 9699690, 223092870, 111546435, 2156564410, 100280245065, 3710369067405, 7420738134810, 6541380665835015
Offset: 1

Views

Author

Donald S. McDonald, May 17 2002

Keywords

Crossrefs

Programs

  • PARI
    t = 0; v = []; for( n = 1, 80, t1 = t; t = t + moebius( n) / n; if( t * t1 < 0, v = concat( v, denominator( t)), )); v

A068337 a(n) = n!*Sum_{k=1..n} mu(k)/k, where mu(k) is the Möbius function.

Original entry on oeis.org

1, 1, 1, 4, -4, 96, -48, -384, -3456, 328320, -17280, -207360, -481697280, -516741120, 79427174400, 1270834790400, 681401548800, 12265227878400, -6169334376038400, -123386687520768000, -158218429759488000, 47610136717000704000
Offset: 1

Views

Author

Leroy Quet, Feb 27 2002

Keywords

Crossrefs

Programs

  • Mathematica
    n = 25; Accumulate[Table[MoebiusMu[k]/k, {k, 1, n}]] * Range[n]! (* Amiram Eldar, Oct 22 2020 *)
  • Python
    from math import factorial
    from functools import lru_cache
    from sympy import harmonic
    @lru_cache(maxsize=None)
    def f(n):
        if n <= 1:
            return 1
        c, j = 1, 2
        k1 = n//j
        while k1 > 1:
            j2 = n//k1 + 1
            c += (harmonic(j-1)-harmonic(j2-1))*f(k1)
            j, k1 = j2, n//j2
        return c+harmonic(j-1)-harmonic(n)
    def A068337(n): return factorial(n)*f(n) # Chai Wah Wu, Nov 03 2023

Formula

a(n) = (-1)^(n-1)*{determinant of the n X n matrix m(i,j) = i+(j (mod i))} - Benoit Cloitre, May 28 2004
From Amiram Eldar, Oct 22 2020: (Start)
a(n) = A000142(n)*A070888(n)/A070889(n).
a(n) ~ O(n! * n^(-1/2 + eps)), for every eps>0, if and only if Riemann's hypothesis is true (Roesler, 1986). (End)

A070890 Numerator of Sum_{k=1..n} mu(k)/k when it changes sign.

Original entry on oeis.org

-1, 2, -1, 19, -1, 304, -81988, 410857, -249979, 4165258, -65721449, 2562470143, -5468849774, 184344882947, -137190436674212, 10026981687881, -12611493192339623, 519973962150962777, -8549627883788520181, 1874648830674470878723, -200643437220052588790575, 877316785444551755504875
Offset: 1

Views

Author

Donald S. McDonald, May 17 2002

Keywords

Examples

			a(1)= -1 because numerator first sign change is 1-1/2-1/3-1/5= > (-1)/30 <0.
a(2)= 2 because next sign change is -1/30+1/6 = 2/15, reverts to positive.
		

Crossrefs

Programs

  • PARI
    t = 0; v = []; for( n = 1, 120, t1 = t; t = t + moebius(n) / n; if( t * t1 < 0, v = concat( v, numerator( t)), )); v
Showing 1-4 of 4 results.