OFFSET
1,1
COMMENTS
Apparently the (ordinary) Dirichlet inverse of A050377. - R. J. Mathar, Jul 15 2010
Also analog of Liouville's function (A008836) in Fermi-Dirac arithmetic, where the terms of A050376 play the role of primes (see examples). - Vladimir Shevelev, Oct 28 2013.
REFERENCES
Vladimir S. Shevelev, Multiplicative functions in the Fermi-Dirac arithmetic, Izvestia Vuzov of the North-Caucasus region, Nature sciences 4 (1996), 28-43 (in Russian)
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
G. L. Cohen, On an integers' infinitary divisors, Math. Comp. 54 (1990), 395-411.
G. L. Cohen and P. Hagis, Jr, Arithmetic functions associated with the infinitary divisors of an integer, Internat. J. Math. Math. Sci. 16 (2) (1993), 373-384.
Simon Litsyn and Vladimir Shevelev, On factorization of integers with restrictions on the exponent, INTEGERS: Electronic Journal of Combinatorial Number Theory, 7 (2007), #A33, 1-36.
Rasa Steuding, Jörn Steuding, and László Tóth, A modified Möbius mu-function, Rendiconti del Circolo Matematico di Palermo, Vol. 60 (2011), pp. 13-21; arXiv preprint, arXiv:1109.4242 [math.NT], 2011.
FORMULA
From Vladimir Shevelev Feb 20 2011: (Start)
Sum_{d runs through i-divisors of n} a(d)=1 if n=1, or 0 if n>1; Sum_{d runs through i-divisors of n} a(d)/d = A091732(n)/n.
Infinitary Moebius inversion:
If Sum_{d runs through i-divisors of n} f(d)=F(n), then f(n) = Sum_{d runs through i-divisors of n} a(d)*F(n/d). (End)
a(n) = (-1)^A064547(n). - R. J. Mathar, Apr 19 2011
Let k=k(n) be the number of terms of A050376 that divide n with odd maximal exponent. Then a(n) = (-1)^k. For example, if n=96, then the maximal exponent of 2 that divides 96 is 5, for 3 it is 1, for 4 it is 2, for 16 it is 1. Thus k(96)=3 and a(96)=-1. - Vladimir Shevelev, Oct 28 2013
From Peter Munn, Jan 25 2020: (Start)
a(n^2) = a(n).
a(A003961(n)) = a(n).
a(A225546(n)) = a(n).
(End)
a(n) = a(A007913(n)) * a(A008833(n)) = (-1)^A001221(A007913(n)) * a(A000188(n)). - Peter Munn, Mar 16 2022
From Amiram Eldar, Dec 23 2023: (Start)
Multiplicative with a(p^e) = (-1)^A000120(e).
Dirichlet g.f.: 1/Product_{k>=0} zeta(2^k * s) (Steuding et al., 2011). (End)
EXAMPLE
G.f. = x - x^2 - x^3 - x^4 - x^5 + x^6 - x^7 + x^8 - x^9 + x^10 - x^11 + x^12 + ...
mu[45]=0 but iMoebiusMu[45]=1 because 45 = 3^2 * 5^1 and the binary digits of 2 and 1 add up to 2, an even number.
A unique representation of 48 over distinct terms of A050376 is 3*16. Since it contains even factors, then a(48)=1; for 54 such a representation is 2*3*9, thus a(54)=-1. - Vladimir Shevelev, Oct 28 2013
MATHEMATICA
iMoebiusMu[n_] := Switch[MoebiusMu[n], 1, 1, -1, -1, 0, If[OddQ[Plus@@(DigitCount[Last[Transpose[FactorInteger[n]]], 2, 1])], -1, 1]];
(* The Moebius inversion formula seems to hold for iMoebiusMu and the infinitary_divisors of n: if g[ n_ ] := Plus@@(f/@iDivisors[ n ]) for all n, then f[ n_ ]===Plus@@(iMoebiusMu[ # ]g[ n/# ])/@iDivisors[ n ]) *)
f[p_, e_] := (-1)^DigitCount[e, 2, 1]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Dec 23 2023 *)
PROG
(PARI) {a(n) = my(A, p, e); if( n<1, 0, A = factor(n); prod(k=1, matsize(A)[1], [p, e] = A[k, ]; (-1) ^ subst( Pol( binary(e)), x, 1)))}; /* Michael Somos, Jan 08 2008 */
(PARI) a(n) = if (n==1, 1, (-1)^omega(core(n)) * a(core(n, 1)[2])) \\ Peter Munn, Mar 16 2022
(PARI) a(n) = vecprod(apply(x -> (-1)^hammingweight(x), factor(n)[, 2])); \\ Amiram Eldar, Dec 23 2023
(Python)
from math import prod
from sympy import factorint
def A064179(n): return prod(-1 if e.bit_count()&1 else 1 for e in factorint(n).values()) # Chai Wah Wu, Oct 12 2024
CROSSREFS
KEYWORD
sign,mult,easy
AUTHOR
Wouter Meeussen, Sep 20 2001
STATUS
approved