login
This site is supported by donations to The OEIS Foundation.

 

Logo

Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A101035 Dirichlet inverse of the gcd-sum function (A018804). 4
1, -3, -5, 1, -9, 15, -13, 1, 4, 27, -21, -5, -25, 39, 45, 1, -33, -12, -37, -9, 65, 63, -45, -5, 16, 75, 4, -13, -57, -135, -61, 1, 105, 99, 117, 4, -73, 111, 125, -9, -81, -195, -85, -21, -36, 135, -93, -5, 36, -48, 165, -25, -105, -12, 189, -13, 185, 171, -117, 45, -121, 183, -52, 1, 225, -315, -133, -33, 225, -351, -141, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

G. P. Michon, Multiplicative Functions.

FORMULA

Multiplicative function with a(p)=1-2p and a(p^e)=(p-1)^2 when e>1 [p prime].

Dirichlet g.f. zeta(s)/zeta^2(s-1). - R. J. Mathar, Apr 10 2011

a(n)=Sum{d|n} tau_{-2}(d)*d, where tau_{-2} is A007427. - Enrique Pérez Herrero, Jan 19 2013

EXAMPLE

a(4)=1, a(8)=1, a(16)=1, a(32)=1, etc. because of the multiplicative definition for powers of 2.

MATHEMATICA

DirichletInverse[f_][1] = 1/f[1]; DirichletInverse[f_][n_] := DirichletInverse[f][n] = -1/f[1]*Sum[ f[n/d]*DirichletInverse[f][d], {d, Most[ Divisors[n]]}]; GCDSum[n_] := Sum[ GCD[n, k], {k, 1, n}]; Table[ DirichletInverse[ GCDSum][n], {n, 1, 72}](* Jean-François Alcover, Dec 12 2011 *)

PROG

(Haskell)

a101035 n = product $ zipWith f (a027748_row n) (a124010_row n) where

   f p 1 = 1 - 2 * p

   f p e = (p - 1) ^ 2

-- Reinhard Zumkeller, Jul 16 2012

CROSSREFS

Cf. A018804, A055615, A046692, A023900, A007427, A053822, A053825, A053826.

Cf. A008683.

Sequence in context: A214229 A214728 A112752 * A204029 A026253 A138259

Adjacent sequences:  A101032 A101033 A101034 * A101036 A101037 A101038

KEYWORD

easy,nice,sign,mult

AUTHOR

Gerard P. Michon, Nov 27 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified August 27 23:31 EDT 2014. Contains 246149 sequences.