A013669 -id:A013669 - cp's OEIS frontend

A015053 Smallest positive integer for which n divides a(n)^6.

1, 2, 3, 2, 5, 6, 7, 2, 3, 10, 11, 6, 13, 14, 15, 2, 17, 6, 19, 10, 21, 22, 23, 6, 5, 26, 3, 14, 29, 30, 31, 2, 33, 34, 35, 6, 37, 38, 39, 10, 41, 42, 43, 22, 15, 46, 47, 6, 7, 10, 51, 26, 53, 6, 55, 14, 57, 58, 59, 30, 61, 62, 21, 2, 65, 66, 67, 34, 69, 70, 71, 6, 73, 74, 15, 38, 77, 78

Offset: 1

R. Muller (Research37(AT)aol.com)

Differs from A007947 as follows: A007947(128)=2, a(128)=4; A007947(256)=2, a(256)=4; A007947(384)=6, a(384)=12; A007947(512)=2, a(512)=4; A007947(640)=10, a(640)=20, etc. - R. J. Mathar, Oct 28 2008

Harvey P. Dale, Table of n, a(n) for n = 1..1000
Henry Bottomley, Some Smarandache-type multiplicative sequences.
Kevin A. Broughan, Restricted divisor sums, Acta Arithmetica, 101(2) (2002), 105-114.
Kevin A. Broughan, Relationship between the integer conductor and k-th root functions, Int. J. Pure Appl. Math. 5(3) (2003), 253-275.
Kevin A. Broughan, Relaxations of the ABC Conjecture using integer k'th roots, New Zealand J. Math. 35(2) (2006), 121-136.
Henry Ibstedt, Surfing on the Ocean of Numbers, Erhus Univ. Press, Vail, 1997.
Eric Weisstein's World of Mathematics, Smarandache Ceil Function.

Cf. A000188 (inner square root), A019554 (outer square root), A053150 (inner 3rd root), A019555 (outer 3rd root), A053164 (inner 4th root), A053166 (outer 4th root), A015052 (5th outer root).

Cf. A013669.

spi[n_]:=Module[{k=1},While[PowerMod[k,6,n]!=0,k++];k]; Array[spi,80] (* Harvey P. Dale, Feb 29 2020 *)
f[p_, e_] := p^Ceiling[e/6]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 18 2020 *)

a(n) = my(f=factor(n)); for (i=1, #f~, f[i,2] = ceil(f[i,2]/6)); factorback(f); \\ Michel Marcus, Feb 15 2015

Multiplicative with a(p^e) = p^ceiling(e/6). - Christian G. Bower, May 16 2005

Sum_{k=1..n} a(k) ~ c * n^2, where c = (zeta(11)/2) * Product_{p prime} (1 - 1/p^2 + 1/p^3 - 1/p^4 + 1/p^5 - 1/p^6 + 1/p^7 - 1/p^8 + 1/p^9 - 1/p^10) = 0.3522558764... . - Amiram Eldar, Oct 27 2022

Corrected by David W. Wilson, Jun 04 2002

A023878 Expansion of Product_{k>=1} (1 - x^k)^(-k^9).

Original entry on oeis.org

1, 1, 513, 20196, 413668, 12444489, 372960863, 9158023846, 223763768245, 5567490203192, 132000248840652, 3018181447183141, 68165389692659690, 1512302997486058542, 32793035921825542778, 698432551205542941608, 14654522099892985823429, 302753023792981375706399

Offset: 0

Olivier Gérard

nonn

In general, column m > 0 of A144048 is asymptotic to (Gamma(m+2)*Zeta(m+2))^((1-2*Zeta(-m))/(2*m+4)) * exp((m+2)/(m+1) * (Gamma(m+2)*Zeta(m+2))^(1/(m+2)) * n^((m+1)/(m+2)) + Zeta'(-m)) / (sqrt(2*Pi*(m+2)) * n^((m+3-2*Zeta(-m))/(2*m+4))). - Vaclav Kotesovec, Mar 01 2015

Seiichi Manyama, Table of n, a(n) for n = 0..995 (first 301 terms from Alois P. Heinz)
G. Almkvist, Asymptotic formulas and generalized Dedekind sums, Exper. Math., 7 (No. 4, 1998), pp. 343-359.
Vaclav Kotesovec, A method of finding the asymptotics of q-series based on the convolution of generating functions, arXiv:1509.08708 [math.CO], Sep 30 2015, p. 21.

Column k=9 of A144048. - Alois P. Heinz, Nov 02 2012

m:=30; R:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[1/(1-x^k)^k^9: k in [1..m]]) )); // G. C. Greubel, Oct 31 2018

with(numtheory):
a:= proc(n) option remember; `if`(n=0, 1,
      add(add(d*d^9, d=divisors(j)) *a(n-j), j=1..n)/n)
    end:
seq(a(n), n=0..20);  # Alois P. Heinz, Nov 02 2012

nmax=30; CoefficientList[Series[Product[1/(1-x^k)^(k^9),{k,1,nmax}],{x,0,nmax}],x] (* Vaclav Kotesovec, Mar 01 2015 *)

m=30; x='x+O('x^m); Vec(prod(k=1, m, 1/(1-x^k)^k^9)) \\ G. C. Greubel, Oct 31 2018

a(n) ~ 3^(67/363) * 5^(67/726) * (7*Zeta(11))^(67/1452) * exp(11 * 3^(4/11) * n^(10/11) * (7*Zeta(11))^(1/11) / (2^(3/11) * 5^(9/11)) + Zeta'(-9)) / (2^(95/726) * sqrt(11*Pi) * n^(793/1452)), where Zeta(11) = A013669 = 1.00049418860411946..., Zeta'(-9) = (5*(7129/2520 - gamma - log(2*Pi))/66 + 14175*Zeta'(10) / (2*Pi^10))/10 = 0.00313014531978857275492576829... . - Vaclav Kotesovec, Feb 27 2015
G.f.: exp( Sum_{n>=1} sigma_10(n)*x^n/n ). - Seiichi Manyama, Mar 05 2017
a(n) = (1/n)*Sum_{k=1..n} sigma_10(k)*a(n-k). - Seiichi Manyama, Mar 05 2017

Definition corrected by Franklin T. Adams-Watters and R. J. Mathar, Dec 04 2006

A321555 a(n) = Sum_{d|n} (-1)^(n/d+1)*d^10.

Original entry on oeis.org

1, 1023, 59050, 1047551, 9765626, 60408150, 282475250, 1072692223, 3486843451, 9990235398, 25937424602, 61857886550, 137858491850, 288972180750, 576660215300, 1098436836351, 2015993900450, 3567040850373, 6131066257802, 10229991281926, 16680163512500, 26533985367846, 41426511213650, 63342475768150

Offset: 1

N. J. A. Sloane, Nov 23 2018

Seiichi Manyama, Table of n, a(n) for n = 1..10000
J. W. L. Glaisher, On the representations of a number as the sum of two, four, six, eight, ten, and twelve squares, Quart. J. Math. 38 (1907), 1-62 (see p. 4 and p. 8).
Index entries for sequences mentioned by Glaisher.

Cf. A321543 - A321565, A321807 - A321836 for similar sequences.

Cf. A013669.

f[p_, e_] := (p^(10*e + 10) - 1)/(p^10 - 1); f[2, e_] := (511*2^(10*e + 1) + 1)/1023; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 50] (* Amiram Eldar, Nov 11 2022 *)

apply( A321555(n)=sumdiv(n, d, (-1)^(n\d-1)*d^10), [1..30]) \\ M. F. Hasler, Nov 26 2018

G.f.: Sum_{k>=1} k^10*x^k/(1 + x^k). - Seiichi Manyama, Nov 25 2018
From Amiram Eldar, Nov 11 2022: (Start)
Multiplicative with a(2^e) = (511*2^(10*e+1)+1)/1023, and a(p^e) = (p^(10*e+10) - 1)/(p^10 - 1) if p > 2.
Sum_{k=1..n} a(k) ~ c * n^11, where c = 93*zeta(11)/1024 = 0.0908651... . (End)

A308637 Decimal expansion of Pi^3/Zeta(3).

Original entry on oeis.org

2, 5, 7, 9, 4, 3, 5, 0, 1, 6, 6, 6, 1, 8, 6, 8, 4, 0, 1, 8, 5, 5, 8, 6, 3, 6, 5, 7, 9, 3, 9, 6, 5, 1, 3, 2, 9, 0, 0, 5, 0, 9, 5, 2, 3, 2, 7, 1, 3, 1, 2, 2, 6, 0, 7, 0, 6, 1, 4, 0, 2, 1, 3, 4, 0, 6, 4, 9, 4, 3, 4, 9, 1, 3, 4, 9, 2, 5, 0, 6, 1, 4, 1, 2, 2, 5, 1

Offset: 2

Seiichi Manyama, Aug 23 2019

Index entries for zeta function.

-----+---------------------------------
   n |  Zeta(n)
-----+---------------------------------
   2 |     Pi^2  / 6         = A013661.
   3 |     Pi^3  / 25.79...  = A002117.
   4 |     Pi^4  / 90        = A013662.
   5 |     Pi^5  / A309926   = A013663.
   6 |     Pi^6  / 945       = A013664.
   7 |     Pi^7  / A309927   = A013665.
   8 |     Pi^8  / 9450      = A013666.
   9 |     Pi^9  / A309928   = A013667.
  10 |     Pi^10 / 93555     = A013668.
  11 |     Pi^11 / A309929   = A013669.
  12 | 691*Pi^12 / 638512875 = A013670.
...
Cf. A002432, A091925, A276120 (Zeta(3)/Pi^3).

RealDigits[Pi^3/Zeta[3], 10, 100][[1]] (* Amiram Eldar, Aug 24 2019 *)

PARI
```
Pi^3/zeta(3)
```

Pi^3/Zeta(3) = A091925/A002117.

More terms from Amiram Eldar, Aug 24 2019

A373105 a(n) = sigma_10(n^2)/sigma_5(n^2).

Original entry on oeis.org

1, 993, 58807, 1016801, 9762501, 58395351, 282458443, 1041204193, 3472494301, 9694163493, 25937263551, 59795016407, 137858120557, 280481233899, 574103396307, 1066193093601, 2015992480593, 3448186840893, 6131063781703, 9926520779301

Offset: 1

Seiichi Manyama, May 25 2024

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

Cf. A057660, A084218, A084220, A372966.
Cf. A371491, A371878, A373007, A373103.
Cf. A013664, A013669.

f[p_, e_] := (p^(10*e+5) + 1)/(p^5 + 1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 20] (* Amiram Eldar, May 25 2024 *)

PARI
```
a(n) = sigma(n^2, 10)/sigma(n^2, 5);
```

a(n) = sumdiv(n, d, moebius(n/d)*(n/d)^5*sigma(d, 10));

a(n) = Sum_{1 <= x_1, x_2, x_3, x_4, x_5 <= n} ( n/gcd(x_1, x_2, x_3, x_4, x^5, n) )^5.
a(n) = Sum_{d|n} mu(n/d) * (n/d)^5 * sigma_10(d).
From Amiram Eldar, May 25 2024: (Start)
Multiplicative with a(p^e) = (p^(10*e+5) + 1)/(p^5 + 1).
Dirichlet g.f.: zeta(s)*zeta(s-10)/zeta(s-5).
Sum_{k=1..n} a(k) ~ c * n^11 / 11, where c = zeta(11)/zeta(6) = 0.9834383562... . (End)

A160960 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 12.

Original entry on oeis.org

1, 2047, 88573, 2096128, 12207031, 181308931, 329554457, 2146435072, 5230147077, 24987792457, 28531167061, 185660345344, 149346699503, 674597973479, 1081213356763, 2197949513728, 2141993519227, 10706111066619, 6471681049901, 25587499475968, 29189626919861, 58403298973867

Offset: 1

N. J. A. Sloane, Nov 19 2009

a(n) is the number of lattices L in Z^11 such that the quotient group Z^11 / L is C_n. - Álvar Ibeas, Nov 26 2015

Álvar Ibeas, Table of n, a(n) for n = 1..10000
Jin Ho Kwak and Jaeun Lee, Enumeration of graph coverings, surface branched coverings and related group theory, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161. See p. 134.
Index to Jordan function ratios J_k/J_1.

Column 11 of A263950.

Cf. A000010, A000203, A008683, A013668, A013669.

b = 12; Table[Sum[MoebiusMu[n/d] d^(b - 1)/EulerPhi@ n, {d, Divisors@ n}], {n, 18}] (* Michael De Vlieger, Nov 27 2015 *)
f[p_, e_] := p^(10*e - 10) * (p^11-1) / (p-1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 25] (* Amiram Eldar, Nov 08 2022 *)

vector(100, n, sumdiv(n^10, d, if(ispower(d, 11), moebius(sqrtnint(d, 11))*sigma(n^10/d), 0))) \\ Altug Alkan, Nov 26 2015

a(n) = {my(f = factor(n)); prod(i = 1, #f~, (f[i,1]^11 - 1)*f[i,1]^(10*f[i,2] - 10)/(f[i,1] - 1));} \\ Amiram Eldar, Nov 08 2022

a(n) = J_11(n)/J_1(n) where J_11 and J_1(n) = A000010(n) are Jordan functions. - R. J. Mathar, Jul 12 2011
From Álvar Ibeas, Nov 26 2015: (Start)
Multiplicative with a(p^e) = p^(10e-10) * (p^11-1) / (p-1).
For squarefree n, a(n) = A000203(n^10). (End)
From Amiram Eldar, Nov 08 2022: (Start)
Sum_{k=1..n} a(k) ~ c * n^11, where c = (1/11) * Product_{p prime} (1 + (p^10-1)/((p-1)*p^11)) = 0.1766326404... .
Sum_{k>=1} 1/a(k) = zeta(10)*zeta(11) * Product_{p prime} (1 - 2/p^11 + 1/p^21) = 1.0005003781952... . (End)
a(n) = (1/n) * Sum_{d|n} mu(n/d)*sigma(d^11). - Ridouane Oudra, Apr 02 2025

Definition corrected by Enrique Pérez Herrero, Oct 30 2010

A160972 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 13.

Original entry on oeis.org

1, 4095, 265720, 8386560, 61035156, 1088123400, 2306881200, 17175674880, 47071500840, 249938963820, 313842837672, 2228476723200, 1941507093540, 9446678514000, 16218261652320, 35175782154240, 36413889826860, 192757795939800, 122961939948120, 511874997903360, 612984472464000

Offset: 1

N. J. A. Sloane, Nov 19 2009

a(n) is the number of lattices L in Z^12 such that the quotient group Z^12 / L is C_n. - Álvar Ibeas, Nov 26 2015

Álvar Ibeas, Table of n, a(n) for n = 1..10000
Jin Ho Kwak and Jaeun Lee, Enumeration of graph coverings, surface branched coverings and related group theory, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161. See p. 134.
Index to Jordan function ratios J_k/J_1.

Column 12 of A263950.

Cf. A000010, A000203, A008683, A013669, A013670.

b = 13; Table[Sum[MoebiusMu[n/d] d^(b - 1)/EulerPhi@ n, {d, Divisors@ n}], {n, 17}] (* Michael De Vlieger, Nov 27 2015 *)
f[p_, e_] := p^(11*e - 11) * (p^12-1) / (p-1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 20] (* Amiram Eldar, Nov 08 2022 *)

vector(100, n, sumdiv(n^11, d, if(ispower(d, 12), moebius(sqrtnint(d, 12))*sigma(n^11/d), 0))) \\ Altug Alkan, Nov 26 2015

a(n) = {my(f = factor(n)); prod(i = 1, #f~, (f[i,1]^12 - 1)*f[i,1]^(11*f[i,2] - 11)/(f[i,1] - 1));} \\ Amiram Eldar, Nov 08 2022

a(n) = J_12(n)/J_1(n) where J_12 and J_1(n) = A000010(n) are Jordan functions. - R. J. Mathar, Jul 12 2011
From Álvar Ibeas, Nov 26 2015: (Start)
Multiplicative with a(p^e) = p^(11e-11) * (p^12-1) / (p-1).
For squarefree n, a(n) = A000203(n^11). (End)
From Amiram Eldar, Nov 08 2022: (Start)
Sum_{k=1..n} a(k) ~ c * n^12, where c = (1/12) * Product_{p prime} (1 + (p^11-1)/((p-1)*p^12)) = 0.1619398772... .
Sum_{k>=1} 1/a(k) = zeta(11)*zeta(12) * Product_{p prime} (1 - 2/p^12 + 1/p^23) = 1.0002481006668... . (End)
a(n) = (1/n) * Sum_{d|n} mu(n/d)*sigma(d^12). - Ridouane Oudra, Apr 02 2025

Definition corrected by Enrique Pérez Herrero, Oct 30 2010

A321814 Sum of 10th powers of odd divisors of n.

Original entry on oeis.org

1, 1, 59050, 1, 9765626, 59050, 282475250, 1, 3486843451, 9765626, 25937424602, 59050, 137858491850, 282475250, 576660215300, 1, 2015993900450, 3486843451, 6131066257802, 9765626, 16680163512500, 25937424602, 41426511213650, 59050

Offset: 1

N. J. A. Sloane, Nov 24 2018

Seiichi Manyama, Table of n, a(n) for n = 1..10000
J. W. L. Glaisher, On the representations of a number as the sum of two, four, six, eight, ten, and twelve squares, Quart. J. Math. 38 (1907), 1-62 (see p. 4 and p. 8).
Eric Weisstein's World of Mathematics, Odd Divisor Function.
Index entries for sequences mentioned by Glaisher.

Column k=10 of A285425.
Cf. A050999, A051000, A051001, A051002, A321810 - A321816 (analog for 2nd .. 12th powers).
Cf. A321543 - A321565, A321807 - A321836 for related sequences.
Cf. A000265, A013669, A013958.

a[n_] := DivisorSum[n, #^10 &, OddQ[#] &]; Array[a, 20] (* Amiram Eldar, Dec 07 2018 *)

apply( A321814(n)=sigma(n>>valuation(n,2),10), [1..30]) \\ M. F. Hasler, Nov 26 2018

from sympy import divisor_sigma
def A321814(n): return int(divisor_sigma(n>>(~n&n-1).bit_length(),10)) # Chai Wah Wu, Jul 16 2022

a(n) = A013958(A000265(n)) = sigma_10(odd part of n); in particular, a(2^k) = 1 for all k >= 0. - M. F. Hasler, Nov 26 2018
G.f.: Sum_{k>=1} (2*k - 1)^10*x^(2*k-1)/(1 - x^(2*k-1)). - Ilya Gutkovskiy, Dec 07 2018
From Amiram Eldar, Nov 02 2022: (Start)
Multiplicative with a(2^e) = 1 and a(p^e) = (p^(10*e+10)-1)/(p^10-1) for p > 2.
Sum_{k=1..n} a(k) ~ c * n^11, where c = zeta(11)/22 = 0.045477... . (End)

A016847 a(n) = (4n+3)^11.

Original entry on oeis.org

177147, 1977326743, 285311670611, 8649755859375, 116490258898219, 952809757913927, 5559060566555523, 25408476896404831, 96549157373046875, 317475837322472439, 929293739471222707, 2472159215084012303, 6071163615208263051, 13931233916552734375

Offset: 0

N. J. A. Sloane

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (12,-66,220,-495,792,-924,792,-495,220,-66,12,-1).

Cf. A004767, A013669.

[(4*n+3)^11: n in [0..20]]; // Vincenzo Librandi, Apr 27 2014

(4*Range[0,20]+3)^11 (* Harvey P. Dale, Apr 26 2014 *)
Table[((4 n + 3)^11), {n, 0, 20}] (* Vincenzo Librandi, Apr 27 2014 *)

a(n) = A004767(n)^11. - Michel Marcus, Apr 27 2014

Sum_{n>=0} 1/a(n) = 2047*zeta(11)/4096 - 50521*Pi^11/29727129600. - Amiram Eldar, Apr 24 2023

A017683 Numerator of sum of -10th powers of divisors of n.

Original entry on oeis.org

1, 1025, 59050, 1049601, 9765626, 30263125, 282475250, 1074791425, 3486843451, 200195333, 25937424602, 10329823175, 137858491850, 144768565625, 23066408612, 1100586419201, 2015993900450, 3574014537275, 6131066257802, 5125005407613, 16680163512500, 13292930108525

Offset: 1

N. J. A. Sloane

Sum_{d|n} 1/d^k is equal to sigma_k(n)/n^k. So sequences A017665-A017712 also give the numerators and denominators of sigma_k(n)/n^k for k = 1..24. The power sums sigma_k(n) are in sequences A000203 (k=1), A001157-A001160 (k=2,3,4,5), A013954-A013972 for k = 6,7,...,24. - Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 05 2001

			1, 1025/1024, 59050/59049, 1049601/1048576, 9765626/9765625, 30263125/30233088, 282475250/282475249, ...

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

Cf. A017684 (denominator), A013668, A013669.

[Numerator(DivisorSigma(10,n)/n^10): n in [1..20]]; // G. C. Greubel, Nov 07 2018

Table[Numerator[Total[Divisors[n]^-10]],{n,20}] (* Harvey P. Dale, Sep 04 2018 *)
Table[Numerator[DivisorSigma[10, n]/n^10], {n, 1, 20}] (* G. C. Greubel, Nov 07 2018 *)

vector(20, n, numerator(sigma(n, 10)/n^10)) \\ G. C. Greubel, Nov 07 2018

Numerators of coefficients in expansion of Sum_{k>=1} x^k/(k^10*(1 - x^k)). - Ilya Gutkovskiy, May 25 2018
From Amiram Eldar, Apr 02 2024: (Start)
sup_{n>=1} a(n)/A017684(n) = zeta(10) (A013668).
Dirichlet g.f. of a(n)/A017684(n): zeta(s)*zeta(s+10).
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k)/A017684(k) = zeta(11) (A013669). (End)

cp's OEIS Frontend

A015053 Smallest positive integer for which n divides a(n)^6.

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A023878 Expansion of Product_{k>=1} (1 - x^k)^(-k^9).

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A321555 a(n) = Sum_{d|n} (-1)^(n/d+1)*d^10.

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A308637 Decimal expansion of Pi^3/Zeta(3).

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A373105 a(n) = sigma_10(n^2)/sigma_5(n^2).

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A160960 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 12.

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A160972 a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 13.

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