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A023900 Dirichlet inverse of Euler totient function (A000010). 45
1, -1, -2, -1, -4, 2, -6, -1, -2, 4, -10, 2, -12, 6, 8, -1, -16, 2, -18, 4, 12, 10, -22, 2, -4, 12, -2, 6, -28, -8, -30, -1, 20, 16, 24, 2, -36, 18, 24, 4, -40, -12, -42, 10, 8, 22, -46, 2, -6, 4, 32, 12, -52, 2, 40, 6, 36, 28, -58, -8, -60, 30, 12, -1, 48, -20, -66, 16, 44, -24, -70, 2, -72, 36, 8, 18, 60, -24, -78, 4, -2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also called reciprocity balance of n.

Apart from different signs, same as sum( d divides n,core(d)*mu(n/d)), where core(d) (A007913) is the squarefree part of d. - Benoit Cloitre, Apr 06 2002

Row sums of triangle A143256. - Gary W. Adamson, Aug 02 2008

Main diagonal of A191898. - Mats Granvik, Jun 19 2011

REFERENCES

T. M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 37.

D. M. Burton, Elementary Number Theory, Allyn and Bacon Inc. Boston, MA, 1976, p. 125.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

G. P. Brown, Some comments on inverse arithmetic functions, Math. Gaz. 89 (516) (2005) 403-408.

K. Dohmen, M. Trinks, An Abstraction of Whitney's Broken Circuit Theorem, arXiv preprint arXiv:1404.5480 [math.CO], 2014.

R. Kemp, On the number of words in the language {w in Sigma* | w = w^R }^2, Discrete Math., 40 (1982), 225-234.

FORMULA

a(n) = Sum_{ d divides n } d*mu(d) = Product_{p|n} (1-p).

a(n) = 1 / (sum_{ d divides n } mu(d)*d/phi(d)).

Dirichlet g.f.: zeta(s)/zeta(s-1). - Michael Somos, Jun 04 2000

a(n+1) = det(n+1)/det(n) where det(n) is the determinant of the n X n matrix M_(i, j) = i/gcd(i, j) = lcm(i, j)/j. - Benoit Cloitre, Aug 19 2003

a(n) = -phi(n)*moebius(A007947(n))*A007947(n)/n. Logarithmic g.f.: Sum_{n >= 1} a(n)*x^n/n = log(F(x)) where F(x) is the g.f. of A117209 and satisfies: 1/(1-x) = product_{n >= 1} F(x^n). - Paul D. Hanna, Mar 03 2006

G.f.: A(x) = sum_{k >= 1} mu(k) k x^k/(1 - x^k) where mu(k) is the Moebius (Mobius) function, A008683. - Stuart Clary, Apr 15 2006

G.f.: A(x) is x times the logarithmic derivative of A117209(x). - Stuart Clary, Apr 15 2006

Row sums of triangle A134842. - Gary W. Adamson, Nov 12 2007

G.f.: x/(1-x) = Sum_{n >= 1} a(n)*x^n/(1-x^n)^2. - Paul D. Hanna, Aug 16 2008

a(n) = phi(rad(n)) *(-1)^omega(n) = A000010(A007947(n)) *(-1)^A001221(n). - Enrique Pérez Herrero, Aug 24 2010

a(n) = Product_{i = 2..n} (1-i)^( (pi(i)-pi(i-1)) * floor( (cos(n*Pi/i))^2 ) ), where pi = A000720, Pi = A000796. - Wesley Ivan Hurt, May 24 2013

a(n) = -limit of zeta(s)*(sum_{d divides n} moebius(d)/exp(d)^(s-1)) as s->1 for n>1. - Mats Granvik, Jul 31 2013

a(n) = sum_{d divides n} mu(d)* rad(d), where rad is A007947. - Enrique Pérez Herrero, May 29 2014.

Conjecture for n>1: Let n = 2^(A007814(n))*m = 2^(ruler(n))*odd_part(n), where m = A000265(n), then a(n) = (-1)^(m=n)*(0+Sum_{i=1..m and gcd(i,m)=1} (4*min(i,m-i)-m)) = (-1)^(m<n)*(1+Sum_{i=1..m and gcd(i,m)>1} (4*min(i,m-i)-m)). - I. V. Serov, May 02 2017

EXAMPLE

x - x^2 - 2*x^3 - x^4 - 4*x^5 + 2*x^6 - 6*x^7 - x^8 - 2*x^9 + 4*x^10 - ...

MAPLE

A023900 := n -> mul(1-i, i=numtheory[factorset](n)); # Peter Luschny, Oct 26 2010

MATHEMATICA

a[ n_] := If[ n < 1, 0, Sum[ d MoebiusMu @ d, { d, Divisors[n]}]] (* Michael Somos, Jul 18 2011 *)

Array[ Function[ n, 1/Plus @@ Map[ #*MoebiusMu[ # ]/EulerPhi[ # ]&, Divisors[ n ] ] ], 90 ]

nmax = 81; Drop[ CoefficientList[ Series[ Sum[ MoebiusMu[k] k x^k/(1 - x^k), {k, 1, nmax} ], {x, 0, nmax} ], x ], 1 ] (* Stuart Clary, Apr 15 2006 *)

t[n_, 1] = 1; t[1, k_] = 1; t[n_, k_] :=  t[n, k] = If[n < k, If[n > 1 && k > 1, Sum[-t[k - i, n], {i, 1, n - 1}], 0], If[n > 1 && k > 1, Sum[-t[n - i, k], {i, 1, k - 1}], 0]]; Table[t[n, n], {n, 36}] (* Mats Granvik, Robert G. Wilson v, Jun 25 2011 *)

Table[DivisorSum[m, # MoebiusMu[#] &], {m, 90}] (* Jan Mangaldan, Mar 15 2013 *)

PROG

(PARI) {a(n) = direuler( p=2, n, (1 - p*X) / (1 - X))[n]}

(PARI) {a(n) = if( n<1, 0, sumdiv( n, d, d * moebius(d)))} /* Michael Somos, Jul 18 2011 */

(PARI) a(n)=sumdivmult(n, d, d*moebius(d)) \\ Charles R Greathouse IV, Sep 09 2014

(Haskell)

a023900 1 = 1

a023900 n = product $ map (1 -) $ a027748_row n

-- Reinhard Zumkeller, Jun 01 2015

(Python)

from sympy import divisors, mobius

def a(n): return sum([d*mobius(d) for d in divisors(n)]) # Indranil Ghosh, Apr 29 2017

CROSSREFS

Cf. A000010, A023898, A117209, A134842.

Moebius transform is A055615.

Cf. A027748, A173557.

Sequence in context: A070777 A173614 A173557 * A141564 A239641 A249151

Adjacent sequences:  A023897 A023898 A023899 * A023901 A023902 A023903

KEYWORD

sign,easy,nice,mult

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified June 26 06:03 EDT 2017. Contains 288754 sequences.