A053825 -id:A053825 - cp's OEIS frontend

A046692 Dirichlet inverse of sigma function (A000203).

1, -3, -4, 2, -6, 12, -8, 0, 3, 18, -12, -8, -14, 24, 24, 0, -18, -9, -20, -12, 32, 36, -24, 0, 5, 42, 0, -16, -30, -72, -32, 0, 48, 54, 48, 6, -38, 60, 56, 0, -42, -96, -44, -24, -18, 72, -48, 0, 7, -15, 72, -28, -54, 0, 72, 0, 80, 90, -60, 48, -62, 96, -24, 0, 84, -144, -68, -36, 96, -144, -72, 0, -74, 114, -20, -40, 96, -168

Offset: 1

Andrew R. Feist (arf22540(AT)cmsu2.cmsu.edu)

			a(36) = a(2^2*3^2) = 2*3 = 6.

Tom M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 39.
Andrew R. Feist, Fun With the Sigma-Function, unpub.

Seiichi Manyama, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Andrew Howroyd)
G. P. Brown, Some comments on inverse arithmetic functions, Math. Gaz. 89 (516) (2005) 403-408.

Cf. A000203, A053822, A053825, A053826, A178448.

t := 1; a := proc(n,t) local t1,d; t1 := 0; for d from 1 to n do if n mod d = 0 then t1 := t1+d^t*mobius(d)*mobius(n/d); fi; od; t1; end;

a[n_] := (k = 0; Do[If[Mod[n, d] == 0, k = k + d*MoebiusMu[d]*MoebiusMu[n/d]], {d, 1, n}]; k); Table[a[n], {n, 1, 78}](* Jean-François Alcover, Oct 13 2011, after Maple *)
f[p_, e_] := Which[e == 1, -p-1, e == 2, p, e >= 3, 0]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 16 2020 *)

a(n)=if(n<1,0,direuler(p=2,n,(1-X)*(1-p*X))[n]) /* Ralf Stephan */

seq(n)={dirdiv(vector(n, n, n==1), vector(n, n, sigma(n)))} \\ Andrew Howroyd, Aug 05 2018

a(p) = -p-1, a(p^2) = p, a(p^k) = 0 for k > 2.
Dirichlet g.f.: 1/(zeta(s)*zeta(s-1)). - Benedict W. J. Irwin, Jul 10 2018
G.f. A(x) satisfies: A(x) = x - Sum_{k>=2} sigma(k)*A(x^k). - Ilya Gutkovskiy, May 11 2019
From Peter Bala, Jan 17 2024: (Start)
a(n) = Sum_{d divides n} d*mu(d)*mu(n/d). See Brown, p. 408.
a(n) = - Sum_{d divides n, d < n} a(d)*sigma_1(n/d).
a(n) = Sum_{d divides n} d*a(d)*J_2(n/d), where the Jordan totient function J_2(n) = A007434(n).
a(n) = Sum_{d divides n} d*A007427(d)*phi(n/d), where A007427 is the Dirichlet inverse of the tau function.
More generally, a(n) = Sum_{d divides n} d*sigma_[r]^(-1)(d)*J_(r+1)(n/d), where sigma_[r]^(-1) denotes the Dirichlet inverse of the function sigma_[r] = Sum_{d divides n} d^r.
a(n) = Sum_{k = 1..n} gcd(k, n)*A007427(gcd(k, n)).
a(n) = Sum_{1 <= j, k <= n} gcd(j, k, n)*a(gcd(j, k, n)). (End)
Sum_{k=1..n} abs(a(k)) ~ 45*n^2/Pi^4. - Vaclav Kotesovec, May 30 2024

Corrected by T. D. Noe, Nov 13 2006

A101035 Dirichlet inverse of the gcd-sum function (A018804).

Original entry on oeis.org

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

Offset: 1

Gerard P. Michon, Nov 27 2004

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

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
G. P. Michon, Multiplicative Functions.

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

Cf. A008683.

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

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 *)
f[p_, e_] := If[e == 1, 1 - 2*p, (p - 1)^2]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Dec 06 2022 *)

seq(n)={dirdiv(vector(n, n, n==1), vector(n, n, sumdiv(n, d, n*eulerphi(d)/d)))} \\ Andrew Howroyd, Aug 05 2018

for(n=1, 100, print1(direuler(p=2, n, (1 - p*X)^2/(1 - X))[n], ", ")) \\ Vaclav Kotesovec, Aug 22 2021

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
Conjecture: Logarithmic g.f. Sum_{n>0,k>0} mu(n)*mu(k)*log(1/(1-x^(n*k))). - Benedict W. J. Irwin, Jul 26 2017

A053822 Dirichlet inverse of sigma_2 function (A001157).

Original entry on oeis.org

1, -5, -10, 4, -26, 50, -50, 0, 9, 130, -122, -40, -170, 250, 260, 0, -290, -45, -362, -104, 500, 610, -530, 0, 25, 850, 0, -200, -842, -1300, -962, 0, 1220, 1450, 1300, 36, -1370, 1810, 1700, 0, -1682, -2500, -1850, -488, -234, 2650, -2210, 0, 49, -125, 2900, -680

Offset: 1

N. J. A. Sloane, Apr 08 2000

sigma_2(n) is the sum of the squares of the divisors of n (A001157).

Tom M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 39.

Robert Israel, Table of n, a(n) for n = 1..10000

Dirichlet inverse of sigma_k(n): A007427 (k = 0), A046692 (k = 1), A053825 (k = 3), A053826 (k = 4), A178448 (k = 5).

Cf. A001157,.

f1:= proc(p,e) if e = 1 then -1-p^2 elif e=2 then p^2 else 0 fi end proc:
f:= n -> mul(f1(t[1],t[2]),t=ifactors(n)[2]);
map(f, [$1..100]); # Robert Israel, Jan 29 2018

a[n_] := Sum[MoebiusMu[n/d] MoebiusMu[d] d^2, {d, Divisors[n]}];
Array[a, 100] (* Jean-François Alcover, Mar 05 2019, after Ilya Gutkovskiy *)
f[p_, e_] := If[e == 1, -p^2 - 1, If[e == 2, p^2, 0]]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 16 2020 *)

seq(n)={dirdiv(vector(n, n, n==1), vector(n, n, sigma(n, 2)))} \\ Andrew Howroyd, Aug 05 2018

for(n=1, 100, print1(direuler(p=2, n, (1 - X)*(1 - p^2*X))[n], ", ")) \\ Vaclav Kotesovec, Sep 16 2020

Dirichlet g.f.: 1/(zeta(s)*zeta(s-2)).
Multiplicative with a(p^1) = -1-p^2, a(p^2) = p^2, a(p^e) = 0 for e>=3. - Mitch Harris, Jun 27 2005
a(n) = Sum_{d|n} mu(n/d)*mu(d)*d^2. - Ilya Gutkovskiy, Nov 06 2018
From Peter Bala, Jan 26 2024: (Start)
a(n) = Sum_{d divides n} d * (sigma(d))^(-1) * phi(n/d), where (sigma(n))^(-1) = A046692(n) denotes the Dirichlet inverse of sigma(n) = A000203(n).
a(n) = Sum_{d divides n} d^2 * (sigma_k(d))^(-1) * J_(k+2)(n/d) for k >= 0, where (sigma_k(n))^(-1) denotes the Dirichlet inverse of the divisor sum function sigma_k(n) and J_k(n) denotes the Jordan totient function. (End)

A053826 Dirichlet inverse of sigma_4 function (A001159).

Original entry on oeis.org

1, -17, -82, 16, -626, 1394, -2402, 0, 81, 10642, -14642, -1312, -28562, 40834, 51332, 0, -83522, -1377, -130322, -10016, 196964, 248914, -279842, 0, 625, 485554, 0, -38432, -707282, -872644, -923522, 0, 1200644, 1419874, 1503652, 1296, -1874162

Offset: 1

N. J. A. Sloane, Apr 08 2000

sigma_4(n) is the sum of the 4th powers of the divisors of n (A001159).

Tom M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 39.

G. C. Greubel, Table of n, a(n) for n = 1..10000

Dirichlet inverse of sigma_k(n): A007427 (k = 0), A046692 (k = 1), A053822(k = 2), A053825 (k = 3), A178448 (k = 5).

Cf. A001159, A046099 (where a(n) = 0).

Table[DivisorSum[n, MoebiusMu[n/#]*MoebiusMu[#]*#^4  &], {n, 1, 50}] (* G. C. Greubel, Nov 07 2018 *)
f[p_, e_] := If[e == 1, -p^4 - 1, If[e == 2, p^4, 0]]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 16 2020 *)

a(n) = sumdiv(n, d, moebius(n/d)*moebius(d)*d^4); \\ Michel Marcus, Nov 06 2018

for(n=1, 100, print1(direuler(p=2, n, (1 - X)*(1 - p^4*X))[n], ", ")) \\ Vaclav Kotesovec, Sep 16 2020

Dirichlet g.f.: 1/(zeta(s)*zeta(s-4)).
Multiplicative with a(p^1) = -1 - p^4, a(p^2) = p^4, a(p^e) = 0 for e>=3. - Mitch Harris, Jun 27 2005
a(n) = Sum_{d|n} mu(n/d)*mu(d)*d^4. - Ilya Gutkovskiy, Nov 06 2018
From Peter Bala, Jan 17 2024: (Start)
a(n) = Sum_{d divides n} d * A053825(d) * phi(n/d), where the totient function phi(n) = A000010(n).
a(n) = Sum_{d divides n} d^2 * (sigma_2(d))^(-1) * J_2(n/d),
a(n) = Sum_{d divides n} d^3 * (sigma_1(d))^(-1) * J_3(n/d), and for k >= 0,
a(n) = Sum_{d divides n} d^4 * (sigma_k(d))^(-1) * J_(k+4)(n/d), where (sigma_k(n))^(-1) denotes the Dirichlet inverse of the divisor sum function sigma_k(n) and J_k(n) denotes the Jordan totient function. (End)

A173525 a(n) = 1 + A053824(n-1), where A053824 = sum of digits in base 5.

Original entry on oeis.org

1, 2, 3, 4, 5, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 7, 8, 9, 10, 11, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9, 6, 7, 8, 9, 10, 7, 8, 9, 10, 11, 8, 9, 10, 11, 12

Offset: 1

Omar E. Pol, Feb 20 2010

Also: a(n) = A053824(5^k+n-1) in the limit k->infinity, where k plays the role of a row index in A053824. (See the comment by M. F. Hasler for the proof.)
This means: if A053824 is regarded as a triangle then the rows converge to this sequence.
See conjecture in the entry A000120, and the case of base 2 in A063787.
From R. J. Mathar, Dec 09 2010: (Start)
In base b=5, A053824 starts counting up from 1 each time the index wraps around a power of b: A053824(b^k)=1.
Obvious recurrences are A053824(m*b^k+i) = m+A053824(i), 1 <= m < b-1, 0 <= i < b^(k-1).
So A053824 can be decomposed into a triangle T(k,n) = A053824(b^k+n-1), assuming that column indices start at n=1; row lengths are (b-1)*b^k.
There is a self-similarity in these sequences; a sawtooth structure of periodicity b is added algebraically on top of a sawtooth structure of periodicity b^2, on top of a periodicity b^3 etc. This leads to some "fake" finitely periodic substructures in the early parts of each row of T(.,.): often, but not always, a(n+b)=1+a(n). Often, but not always, a(n+b^2)=1+a(n) etc.
The common part of the rows T(.,.) grows with the power of b as shown in the recurrence above, and defines a(n) in the limit of large row indices k. (End)
The two definitions agree because the first 5^r terms in each row correspond to numbers 5^r, 5^r+1,...,5^r+(5^r-1), which are written in base 5 as a leading 1 plus the digits of 0,...,5^r-1. - M. F. Hasler, Dec 09 2010
From Omar E. Pol, Dec 10 2010: (Start)
In the scatter plots of these sequences, the basic structure is an element with b^2 points, where b is the associated base. (Scatter plots are created with the "graph" button of a sequence.) Sketches of these structures look as follows, the horizontal axis a squeezed version of the index n, b consecutive points packed vertically, and the vertical axis a(n):
........................................................
................................................ * .....
............................................... ** .....
..................................... * ...... *** .....
.................................... ** ..... **** .....
.......................... * ...... *** .... ***** .....
......................... ** ..... **** ... ****** .....
............... * ...... *** .... ***** ... ***** ......
.............. ** ..... **** .... **** .... **** .......
.... * ...... *** ..... *** ..... *** ..... *** ........
... ** ...... ** ...... ** ...... ** ...... ** .........
... * ....... * ....... * ....... * ....... * ..........
........................................................
... b=2 ..... b=3 ..... b=4 ..... b=5 ..... b=6 ........
. A000120 . A053735 . A053737 . A053824 . A053827 ......
. A063787 . A173523 . A173524 . A173525 . A173526 ......
........................................................
............................................. * ........
............................................ ** ........
........................... * ............. *** ........
.......................... ** ............ **** ........
........... *............ *** ........... ***** ........
.......... ** .......... **** .......... ****** ........
......... ***.......... ***** ......... ******* ........
........ **** ........ ****** ........ ******** ........
....... ***** ....... ******* ....... ********* ........
...... ****** ...... ******** ....... ******** .........
..... ******* ...... ******* ........ ******* ..........
..... ****** ....... ****** ......... ****** ...........
..... ***** ........ ***** .......... ***** ............
..... **** ......... **** ........... **** .............
..... *** .......... *** ............ *** ..............
..... ** ........... ** ............. ** ...............
..... * ............ * .............. * ................
........................................................
..... b=7 .......... b=8 ............ b=9 ..............
... A053828 ...... A053829 ........ A053830 ............
... A173527 ...... A173528 ........ A173529 ............(End)

Reinhard Zumkeller, Table of n, a(n) for n = 1..3126=5^5+1
Robert Walker, Self Similar Sloth Canon Number Sequences

Cf. A000120, A053824, A063787, A173523, A173524, A173526, A173527, A173528, A173529.

a173525 = (+ 1) . a053824 . (subtract 1) -- Reinhard Zumkeller, Jan 31 2014

A053825 := proc(n) add(d, d=convert(n,base,5)) ; end proc:
A173525 := proc(n) local b,k; b := 5 ; if n < b then n; else k := n/(b-1);   k := ceil(log(k)/log(b)) ; A053825(b^k+n-1) ; end if; end proc:
seq(A173525(n),n=1..100) ;

Total[IntegerDigits[#,5]]+1&/@Range[0,100] (* Harvey P. Dale, Jun 14 2015 *)

A173525(n)={ my(s=1); n--; until(!n\=5, s+=n%5); s } \\ M. F. Hasler, Dec 09 2010

A173525(n)={ my(s=1+(n=divrem(n-1,5))[2]); while((n=divrem(n[1],5))[1],s+=n[2]); s+n[2] } \\ M. F. Hasler, Dec 09 2010

a(n) = A053824(5^k + n - 1) where k >= ceiling(log_5(n/4)). - R. J. Mathar, Dec 09 2010

More terms from Vincenzo Librandi, Aug 02 2010

A189922 Jordan function J_{-4} multiplied by n^4.

Original entry on oeis.org

1, -15, -80, -15, -624, 1200, -2400, -15, -80, 9360, -14640, 1200, -28560, 36000, 49920, -15, -83520, 1200, -130320, 9360, 192000, 219600, -279840, 1200, -624, 428400, -80, 36000, -707280, -748800, -923520, -15, 1171200, 1252800, 1497600, 1200, -1874160

Offset: 1

Wolfdieter Lang, Jun 16 2011

For the Jordan function J_k see the Comtet and Apostol references.

			a(2) = a(4) = a(8) = ... = 1 - 2^4 = -15.
a(4) = mu(1)*1^4 + mu(2)*2^4 + mu(4)*4^4 = 1 - 16 + 0 = -15.
Sum identity for n=4: a(1)*(4/1)^4 + a(2)*(4/2)^4 + a(4)*(4/4)^4 = 256 - 15*16 - 15 = 1.

T. M. Apostol, Introduction to Analytic Number Theory, Springer, 1986.
L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 199, #3.

G. C. Greubel, Table of n, a(n) for n = 1..10000 (terms 1..200 from Indranil Ghosh)

Cf. A023900 (k=-1), A046970 (k=-2), A063453 (k=-3).

a:= n-> mul(1-i[1]^4, i=ifactors(n)[2]):
seq(a(n), n=1..48);  # Alois P. Heinz, Jan 26 2024

a[n_] := Sum[ MoebiusMu[d]*d^4, {d, Divisors[n]}]; Table[a[n], {n, 1, 30}] (* Jean-François Alcover, Sep 03 2012 *)
f[p_, e_] := (1-p^4); a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Dec 08 2020 *)

for (n=1, 30, print1(sumdiv(n, d, moebius(d) * d^4),", ")); \\ Indranil Ghosh, Mar 11 2017

a(n) = J_{-4}(n)*n^4 = Product_{p prime | n} (1 - p^4), for n>=2, a(1)=1.
a(n) = Sum_{d|n} mu(d)*d^4 with the Moebius function mu = A008683.
Dirichlet g.f.: zeta(s)/zeta(s-4).
Sum identity: Sum_{d|n} a(n)*(n/d)^4 = 1 for all n>=1.
a(n) = a(rad(n)) with rad(n) = A007947(n), the squarefree kernel of n.
G.f.: Sum_{k>=1} mu(k)*k^4*x^k/(1 - x^k). - Ilya Gutkovskiy, Jan 15 2017
a(n) = Sum_{d divides n} d * sigma_3(d)^(-1) * sigma_1(n/d), where sigma_3(n)^(-1) = A053825(n) denotes the Dirichlet inverse of sigma_3(n). - Peter Bala, Jan 26 2024

A178448 Dirichlet inverse of A001160, sigma_5.

Original entry on oeis.org

1, -33, -244, 32, -3126, 8052, -16808, 0, 243, 103158, -161052, -7808, -371294, 554664, 762744, 0, -1419858, -8019, -2476100, -100032, 4101152, 5314716, -6436344, 0, 3125, 12252702, 0, -537856, -20511150, -25170552, -28629152, 0, 39296688, 46855314, 52541808

Offset: 1

R. J. Mathar, Dec 22 2010

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A001160, A053825, A053826.

a[1] = 1; a[n_] := a[n] = -Sum[ DivisorSigma[5, n/d] a[d], {d, Most @ Divisors[n]}]; Table[a[n], {n, 1, 29}] (* Jean-François Alcover, Jun 24 2013 *)
f[p_, e_] := If[e == 1, -p^5 - 1, If[e == 2, p^5, 0]]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 16 2020 *)

A178448_vec(len)={
        a063524=vector(len) ; a063524[1] = 1 ;
        a001160=direuler(p=2,len, 1/(1-p^5*X)/(1-X)) ;
        dirdiv(a063524,a001160) ;}
{ A178448_vec(70) } /* R. J. Mathar, Mar 10 2011 */

a(n) = sumdiv(n, d, moebius(n/d)*moebius(d)*d^5); \\ Michel Marcus, Nov 06 2018

for(n=1, 100, print1(direuler(p=2, n, (1 - X)*(1 - p^5*X))[n], ", ")) \\ Vaclav Kotesovec, Sep 16 2020

Dirichlet g.f.: 1/(zeta(s)*zeta(s-5)). - R. J. Mathar, Mar 10 2011
a(n) = Sum_{d|n} mu(n/d)*mu(d)*d^5. - Ilya Gutkovskiy, Nov 06 2018
Multiplicative with a(p) = -1 - p^5, a(p^2) = p^5, and a(p^e) = 0 for e>=3. - Amiram Eldar, Sep 16 2020

More terms from Amiram Eldar, Sep 16 2020

A334659 Dirichlet g.f.: 1 / zeta(s-3).

Original entry on oeis.org

1, -8, -27, 0, -125, 216, -343, 0, 0, 1000, -1331, 0, -2197, 2744, 3375, 0, -4913, 0, -6859, 0, 9261, 10648, -12167, 0, 0, 17576, 0, 0, -24389, -27000, -29791, 0, 35937, 39304, 42875, 0, -50653, 54872, 59319, 0, -68921, -74088, -79507, 0, 0, 97336, -103823, 0, 0, 0, 132651, 0, -148877

Offset: 1

Ilya Gutkovskiy, May 07 2020

Dirichlet inverse of A000578.
Moebius transform of A063453.
Inverse Moebius transform of A053825.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A008683, A055615, A334657, A334660.

Cf. A000578, A053825, A063453.

Mathematica
```
Table[MoebiusMu[n] n^3, {n, 53}]
```

G.f. A(x) satisfies: A(x) = x - 2^3 * A(x^2) - 3^3 * A(x^3) - 4^3 * A(x^4) - ...
a(1) = 1; a(n) = -n^3 * Sum_{d|n, d < n} a(d) / d^3.
a(n) = mu(n) * n^3.
Multiplicative with a(p^e) = -p^3 if e = 1 and 0 otherwise. - Amiram Eldar, Dec 05 2022

A120630 Dirichlet inverse of A002654.

Original entry on oeis.org

1, -1, 0, 0, -2, 0, 0, 0, -1, 2, 0, 0, -2, 0, 0, 0, -2, 1, 0, 0, 0, 0, 0, 0, 1, 2, 0, 0, -2, 0, 0, 0, 0, 2, 0, 0, -2, 0, 0, 0, -2, 0, 0, 0, 2, 0, 0, 0, -1, -1, 0, 0, -2, 0, 0, 0, 0, 2, 0, 0, -2, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, -2, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 4, 0, 0, 0, -2, -2, 0, 0, 0, 0, 0, 0, -2, 1, 0, 0, -2, 0, 0, 0, 0, 2, 0, 0, -2, 0, 0, 0, -2, 0, 0, 0, 2, 0, 0

Offset: 1

Gerard P. Michon, Jun 25 2006

			a(65)=4 because 65 is 5 times 13 and both of those primes are congruent to 1 modulo 4. Doubling an odd index yields the opposite of the value (e.g., a(130)=-4) because a(2)=-1. Doubling an even index yields zero.

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Cf. A002654, A006752, A023900, A046692, A053822, A053825, A053826, A101035.

A120630 := proc(n)
    local a,pp;
    if n = 1 then
        1;
    else
        a := 1 ;
        for pp in ifactors(n)[2] do
            if op(2,pp) > 2 then
                a := 0;
            elif op(1,pp) = 2 then
                if op(2,pp) = 1 then
                    a := -a ;
                else
                    a := 0 ;
                end if;
            elif modp(op(1,pp),4) = 3 then
                if op(2,pp) = 1 then
                    a := 0 ;
                else
                    a := -a ;
                end if;
            else
                if op(2,pp) = 1 then
                    a := -2*a ;
                else
                    ;
                end if;
            end if;
        end do:
        a;
    end if;
end proc: # R. J. Mathar, Sep 15 2015

A120630[n_] := Module[{a, pp}, If[n == 1, 1, a = 1; Do[Which[pp[[2]] > 2, a = 0, pp[[1]] == 2, If[pp[[2]] == 1, a = -a, a = 0], Mod[pp[[1]], 4] == 3, If[pp[[2]] == 1, a = 0, a = -a], True, If[pp[[2]] == 1, a = -2*a]], {pp, FactorInteger[n]}]; a]]; Array[A120630, 120] (* Jean-François Alcover, Apr 24 2017, after R. J. Mathar *)

seq(n)={dirdiv(vector(n, n, n==1), vector(n, n, sumdiv( n, d, (d%4==1) - (d%4==3))))} \\ Andrew Howroyd, Aug 05 2018

Multiplicative function with a(p^e)=0 if e>2. a(2)=-1, a(4)=0. If p is a prime congruent to 3 modulo 4, then a(p)=0 and a(p^2)=-1. If p is a prime congruent to 1 modulo 4, then a(p)=-2 and a(p^2)=1.

Sum_{k=1..n} abs(a(k)) ~ c * n, where c = 3/(2*Pi*G) = 0.521269..., and G is Catalan's constant (A006752). - Amiram Eldar, Jan 22 2024

A347227 Square array T(n,k), n >= 1, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{d|n} mu(d)mu(n/d)d^k.

Original entry on oeis.org

1, 1, -2, 1, -3, -2, 1, -5, -4, 1, 1, -9, -10, 2, -2, 1, -17, -28, 4, -6, 4, 1, -33, -82, 8, -26, 12, -2, 1, -65, -244, 16, -126, 50, -8, 0, 1, -129, -730, 32, -626, 252, -50, 0, 1, 1, -257, -2188, 64, -3126, 1394, -344, 0, 3, 4, 1, -513, -6562, 128, -15626, 8052, -2402, 0, 9, 18, -2

Offset: 1

Seiichi Manyama, Aug 24 2021

			Square array begins:
   1,  1,   1,    1,    1,     1, ...
  -2, -3,  -5,   -9,  -17,   -33, ...
  -2, -4, -10,  -28,  -82,  -244, ...
   1,  2,   4,    8,   16,    32, ...
  -2, -6, -26, -126, -626, -3126, ...
   4, 12,  50,  252, 1394,  8052, ...

Seiichi Manyama, Antidiagonals n = 1..140, flattened

Columns k=0..5 give A007427, A046692, A053822, A053825, A053826, A178448.

T(n,n) gives A347251.

T[n_, k_] := DivisorSum[n, MoebiusMu[#] * MoebiusMu[n/#] * #^k &]; Table[T[n - k + 1, k], {n, 0, 10}, {k, n, 0, -1}] // Flatten (* Amiram Eldar, Aug 24 2021 *)

T(n, k) = sumdiv(n, d, moebius(d)*moebius(n/d)*d^k);

Dirichlet g.f. of column k: 1/(zeta(s)*zeta(s-k)).

cp's OEIS Frontend

A046692 Dirichlet inverse of sigma function (A000203).

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A101035 Dirichlet inverse of the gcd-sum function (A018804).

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A053822 Dirichlet inverse of sigma_2 function (A001157).

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A053826 Dirichlet inverse of sigma_4 function (A001159).

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A173525 a(n) = 1 + A053824(n-1), where A053824 = sum of digits in base 5.

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A189922 Jordan function J_{-4} multiplied by n^4.

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A347227 Square array T(n,k), n >= 1, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{d|n} mu(d)mu(n/d)d^k.