A061503 -id:A061503 - cp's OEIS frontend

A048691 a(n) = d(n^2), where d(k) = A000005(k) is the number of divisors of k.

1, 3, 3, 5, 3, 9, 3, 7, 5, 9, 3, 15, 3, 9, 9, 9, 3, 15, 3, 15, 9, 9, 3, 21, 5, 9, 7, 15, 3, 27, 3, 11, 9, 9, 9, 25, 3, 9, 9, 21, 3, 27, 3, 15, 15, 9, 3, 27, 5, 15, 9, 15, 3, 21, 9, 21, 9, 9, 3, 45, 3, 9, 15, 13, 9, 27, 3, 15, 9, 27, 3, 35, 3, 9, 15, 15, 9, 27, 3, 27

Offset: 1

David Johnson-Davies

Inverse Moebius transform of A034444: Sum_{d|n} 2^omega(d), where omega(n) = A001221(n) is the number of distinct primes dividing n.
Number of elements in the set {(x,y): x|n, y|n, gcd(x,y)=1}.
Number of elements in the set {(x,y): lcm(x,y)=n}.
Also gives total number of positive integral solutions (x,y), order being taken into account, to the optical or parallel resistor equation 1/x + 1/y = 1/n. Indeed, writing the latter as X*Y=N, with X=x-n, Y=y-n, N=n^2, the one-to-one correspondence between solutions (X, Y) and (x, y) is obvious, so that clearly, the solution pairs (x, y) are tau(N)=tau(n^2) in number. - Lekraj Beedassy, May 31 2002
Number of ordered pairs of positive integers (a,c) such that n^2 - ac = 0. Therefore number of quadratic equations of the form ax^2 + 2nx + c = 0 where a,n,c are positive integers and each equation has two equal (rational) roots, -n/a. (If a and c are positive integers, but, instead, the coefficient of x is odd, it is impossible for the equation to have equal roots.) - Rick L. Shepherd, Jun 19 2005
Problem A1 on the 21st Putnam competition in 1960 (see John Scholes link) asked for the number of pairs of positive integers (x,y) such that xy/(x+y) = n: the answer is a(n); for n = 4, the a(4) = 5 solutions (x,y) are (5,20), (6,12), (8,8), (12,6), (20,5). - Bernard Schott, Feb 12 2023
Numbers k such that a(k)/d(k) is an integer are in A217584 and the corresponding quotients are in A339055. - Bernard Schott, Feb 15 2023

A. M. Gleason et al., The William Lowell Putnam Mathematical Competitions, Problems & Solutions:1938-1960 Soln. to Prob. 1 1960, p. 516, MAA, 1980.
Ross Honsberger, More Mathematical Morsels, Morsel 43, pp. 232-3, DMA No. 10 MAA, 1991.
Loren C. Larson, Problem-Solving Through Problems, Prob. 3.3.7, p. 102, Springer 1983.
Alfred S. Posamentier and Charles T. Salkind, Challenging Problems in Algebra, Prob. 9-9 pp. 143 Dover NY, 1988.
D. O. Shklarsky et al., The USSR Olympiad Problem Book, Soln. to Prob. 123, pp. 28, 217-8, Dover NY.
Wacław Sierpiński, Elementary Theory of Numbers, pp. 71-2, Elsevier, North Holland, 1988.
James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, page 91.
Charles W. Trigg, Mathematical Quickies, Question 194, pp. 53, 168, Dover, 1985.

Enrique Pérez Herrero, Table of n, a(n) for n = 1..10000
Ovidiu Bagdasar, On Some Functions Involving the lcm and gcd of Integer Tuples.
Umberto Cerruti, Percorsi tra i numeri (in Italian), pages 3-4.
Daniele A. Gewurz and Francesca Merola, Sequences realized as Parker vectors of oligomorphic permutation groups, J. Integer Seq., Vol. 6 (2003), Article 03.1.6.
John Scholes, Problem A1 of 21st Putnam Competition 1960, 2002. [Wayback Machine link]
Wacław Sierpiński, Elementary Theory of Numbers, Warszawa 1964.
Index to sequences related to Olympiads and other Mathematical competitions.

Cf. A000005, A034444, Mobius transf. of A035116, A048785, A061391, A018805, A002088, A015614, A018892, A063647, A182139.
Partial sums give A061503.
For similar LCM sequences, see A070919, A070920, A070921.
Cf. A005408, A124010.
For the earliest occurrence of 2n-1 see A016017.
Cf. A001620, A082633, A217584, A339055.

a048691 = product . map (a005408 . fromIntegral) . a124010_row
-- Reinhard Zumkeller, Jul 12 2012

A048691[n_]:=DivisorSigma[0,n^2] (* Enrique Pérez Herrero, May 30 2010 *)
DivisorSigma[0,Range[80]^2] (* Harvey P. Dale, Apr 08 2015 *)

numlib::tau (n^2)$ n=1..90 // Zerinvary Lajos, May 13 2008

A048691(n)=prod(i=1,#n=factor(n)[,2],n[i]*2+1) /* or, of course, a(n)=numdiv(n^2) */ \\ M. F. Hasler, Dec 30 2007

for(n=1, 100, print1(direuler(p=2, n, (1 - X^2)/(1 - X)^3)[n], ", ")) \\ Vaclav Kotesovec, Aug 21 2021

[sigma(n**2, 0) for n in range(1, 81)] # Stefano Spezia, Jul 14 2025

a(n) = A000005(A000290(n)).
tau(n^2) = Sum_{d|n} mu(n/d)*tau(d)^2, where mu(n) = A008683(n), cf. A061391.
Multiplicative with a(p^e) = 2e+1. - Vladeta Jovovic, Jul 23 2001
Also a(n) = Sum_{d|n} (tau(d)*moebius(n/d)^2), Dirichlet convolution of A000005 and A008966. - Benoit Cloitre, Sep 08 2002
a(n) = A055205(n) + A000005(n). - Reinhard Zumkeller, Dec 08 2009
Dirichlet g.f.: (zeta(s))^3/zeta(2s). - R. J. Mathar, Feb 11 2011
a(n) = Sum_{d|n} 2^omega(d). Inverse Mobius transform of A034444. - Enrique Pérez Herrero, Apr 14 2012
G.f.: Sum_{k>=1} 2^omega(k)*x^k/(1 - x^k). - Ilya Gutkovskiy, Mar 10 2018
Sum_{k=1..n} a(k) ~ n*(6/Pi^2)*(log(n)^2/2 + log(n)*(3*gamma - 1) + 1 - 3*gamma + 3*gamma^2 - 3*gamma_1 + (2 - 6*gamma - 2*log(n))*zeta'(2)/zeta(2) + (2*zeta'(2)/zeta(2))^2 - 2*zeta''(2)/zeta(2)), where gamma is Euler's constant (A001620) and gamma_1 is the first Stieltjes constant (A082633). - Amiram Eldar, Jan 26 2023

Additional comments from Vladeta Jovovic, Apr 29 2001

A060648 Number of cyclic subgroups of the group C_n X C_n (where C_n is the cyclic group of order n).

Original entry on oeis.org

1, 4, 5, 10, 7, 20, 9, 22, 17, 28, 13, 50, 15, 36, 35, 46, 19, 68, 21, 70, 45, 52, 25, 110, 37, 60, 53, 90, 31, 140, 33, 94, 65, 76, 63, 170, 39, 84, 75, 154, 43, 180, 45, 130, 119, 100, 49, 230, 65, 148, 95, 150, 55, 212, 91, 198, 105, 124, 61, 350, 63, 132, 153, 190

Offset: 1

Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 04 2001

The group U(n) of units modulo n acts on the direct product (Z_n)^k by multiplication. The number g(n,k) of orbits of U(n) acting on Z/(n)^k is g(n,k) = (1/phi(n))*Sum(gcd(n,a-1)^k) where the sum is over a in U(n) and phi(n) is the Euler totient function. A060648 gives g(n,2). - W. Edwin Clark, Jul 20 2001

a(n) is also the number of orbits of length n for the map TxT (Cartesion product) where T is a map with one orbit of each length. - Thomas Ward, Apr 08 2009

			The cycle index of C_4 X C_4 is (x(1)^4 + x(2)^2 + 2*x(4))^2 = x(1)^8 + 2*x(1)^4*x(2)^2 + 4*x(1)^4*x(4) + x(2)^4 + 4*x(2)^2*x(4) + 4*x(4)^2 and C_4 X C_4 has 1 element of order 1, 3 elements of order 2 and 12 elements of order 4. So a(4) = 1/phi(1) + 3/phi(2) + 12/phi(4) = 10, where phi = Euler totient function, cf. A000010. - _Vladeta Jovovic_, Jul 05 2001
For a(4) the pairs (e,d) are (1,4),(2,4),(4,4),(4,2),(4,1) with gcds 1,2,4,2,1 resp. giving 10 in total. - _Thomas Ward_, Apr 08 2009

Enrique Pérez Herrero, Table of n, a(n) for n = 1..5000
M. Hampejs, N. Holighaus, L. Toth and C. Wiesmeyr, On the subgroups of the group Z_m X Z_n, arXiv preprint arXiv:1211.1797 [math.GR], 2012-2014. - From _N. J. A. Sloane_, Jan 02 2013
W. G. Nowak and L. Tóth, On the average number of subgroups of the group Z_m X Z_n, arXiv preprint arXiv:1307.1414 [math.NT], 2013.
Apisit Pakapongpun and Thomas Ward, Functorial orbit counting, Journal of Integer Sequences, 12 (2009) Article 09.2.4.
László Tóth, Menon's identity and arithmetical sums representing functions of several variables, Rend. Sem. Mat. Univ. Politec. Torino, 69 (2011), 97-110, and arXiv:1103.5861, [math.NT], 2011.
László Tóth, On the number of cyclic subgroups of a finite abelian group, arXiv: 1203.6201 [math.GR], 2012.
László Tóth, Multiplicative arithmetic functions of several variables: a survey, arXiv preprint arXiv:1310.7053 [math.NT], 2013-2014.
Index entries for sequences related to groups.

Cf. A060724, A063379, A061503, A064969, A216620, A280184, A344219, A344302, A344303.

for n from 1 to 200 do:ans := 1:for i from 1 to nops(ifactors(n)[2]) do p := ifactors(n)[2][i][1]:e := ifactors(n)[2][i][2]:ans := ans*(p^(e+1)+p^e-2)/(p-1):od:printf(`%d,`,ans):od:

Table[ Plus @@ Map[ Times @@ (EulerPhi /@ #)/EulerPhi[ LCM @@ # ] &, Flatten[ Outer[ {##} &, Divisors[ i ], Divisors[ i ] ], 1 ] ], {i, 1, 100} ]
f[p_, e_] := (p^(e+1)+p^e-2)/(p-1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 20 2020 *)

a(n) = sumdiv(n, d,  2^omega(d)*(n/d) ); \\ Joerg Arndt, Sep 16 2012

def A060648(n) :
    def dedekind_psi(n) : return n*mul(1+1/p for p in prime_divisors(n))
    return reduce(lambda x,y: x+y, [dedekind_psi(d) for d in divisors(n)])
[A060648(n) for n in (1..64)]  # Peter Luschny, Sep 10 2012

a(n) is multiplicative: if the canonical factorization of n is the product of p^e(p) over primes then a(n) = product a(p^e(p)). If n = p^e, p prime, a(n) = (p^(e+1)+p^e-2)/(p-1).
a(n) = Sum_{i|n, j|n} phi(i)*phi(j)/phi(lcm(i, j)). - Vladeta Jovovic, Jul 07 2001
a(n) = Sum_{i|n, j|n} phi(gcd(i, j)).
a(n) = Sum_{d|n} phi(n/d)*tau(d^2).
a(n) = sum(d|n, sigma(d)*moebius(n/d)^2 ). - Benoit Cloitre, Sep 08 2002
Inverse Euler transform of A156302. - Vladeta Jovovic, Feb 14 2009
Moebius transform of A060724. - Vladeta Jovovic, Apr 05 2009
Also a(n) = (1/n)*Sum_{d|n} sigma(d)^2*moebius(n/d). - Vladeta Jovovic, Mar 31 2009
Inverse Moebius transform of A001615. - Vladeta Jovovic, Apr 05 2009
From Thomas Ward, Apr 08 2009: (Start)
a(n) = Sum_{lcm(e,d)=n} gcd(e,d).
Dirichlet g.f.: zeta(s)^2*zeta(s-1)/zeta(2s). (End)
For the proofs of these formulas see the papers of L. Toth.
a(n) = Sum_{d|n} psi(d), where psi is Dedekind's psi function A001615. - Peter Luschny, Sep 10 2012
a(n) = Sum_{d|n} 2^omega(d)*(n/d). - Peter Luschny, Sep 15 2012
Sum_{k=1..n} a(k) ~ (5/4) * n^2. - Amiram Eldar, Oct 19 2022
a(n) = Sum_{k=1..n} tau(gcd(n,k)^2). - Ridouane Oudra, Apr 10 2023
a(n) = Sum_{d divides n} J_2(d)/phi(d) = Sum_{1 <= i, j <= n} 1/phi(n/gcd(i,j,n)), where the Jordan totient function J_2(n) = A007434(n). - Peter Bala, Jan 23 2024

More terms and additional comments from Vladeta Jovovic, Jul 05 2001

A061502 a(n) = Sum_{k<=n} tau(k)^2, where tau = number of divisors function A000005.

Original entry on oeis.org

1, 5, 9, 18, 22, 38, 42, 58, 67, 83, 87, 123, 127, 143, 159, 184, 188, 224, 228, 264, 280, 296, 300, 364, 373, 389, 405, 441, 445, 509, 513, 549, 565, 581, 597, 678, 682, 698, 714, 778, 782, 846, 850, 886, 922, 938, 942, 1042, 1051, 1087

Offset: 1

N. J. A. Sloane, Jun 14 2001

nonn

R. Ayoub, An Introduction to the Analytic Theory of Numbers, Amer. Math. Soc., 1963; Chapter II, Problem 56.

N. J. A. Sloane, Table of n, a(n) for n = 1..1024
Adrian Dudek, On the Success of Mishandling Euclid's Lemma, arXiv:1602.03555 [math.HO], 2016. See B(n) p. 2.
Chaohua Jia and Ayyadurai Sankaranarayanan, The mean square of the divisor function, Acta Arithmetica 164 (2014), 181-208.
Michaela Cully-Hugill and Timothy Trudgian, Two explicit divisor sums, arXiv:1911.07369 [math.NT], Nov 19 2019
Vaclav Kotesovec, Graph - The asymptotic ratio (1000000 terms)
Florian Luca and László Tóth, The r-th moment of the divisor function: an elementary approach, Journal of Integer Sequences 20 (2017), Article 17.7.4, 8 pp.
Adolf Piltz, Über das Gesetz, nach welchem die mittlere Darstellbarkeit der natürlichen Zahlen als Produkte einer gegebenen Anzahl Faktoren mit der Grösse der Zahlen wächst, 1881.
Ramanujan's Papers, Some formulas in the analytic theory of numbers, Messenger of Mathematics, XLV, 1916, 81-84, Formula (3).
D. Suryanarayana and R. Rama Chandra Rao, On an Asymptotic Formula of Ramanujan, Mathematica Scandinavica, 32, 258-264, 1973.
B. M. Wilson, Proofs of some formulas enunciated by Ramanujan, Proc. London Math. Soc. (2) 21 (1922) 235-255.

Cf. A000005, A035116, A061503, A318755.
Cf. A092742 (A), A245074 (B), A319090 (C), A319091 (D).
Cf. A057434, A072379, A074789.

[&+[NumberOfDivisors(k^2)*Floor(n/k): k in [1..n]]: n in [1..60]]; // Vincenzo Librandi, Sep 10 2016

Table[Sum[DivisorSigma[0, k^2]*Floor[n/k], {k, 1, n}], {n, 1, 50}] (* Vaclav Kotesovec, Aug 30 2018 *)
Accumulate[Table[DivisorSigma[0, n]^2, {n, 1, 50}]] (* Vaclav Kotesovec, Sep 10 2018 *)

for (n=1, 1024, write("b061502.txt", n, " ", sum(k=1, n, numdiv(k)^2)) ) \\ Harry J. Smith, Jul 23 2009

vector(60, n, sum(k=1, n, numdiv(k)^2)) \\ Michel Marcus, Jul 23 2015

first(n)=my(v=vector(n),s); forfactored(k=1,n, v[k[1]] = s += numdiv(k)^2); v; \\ Charles R Greathouse IV, Nov 28 2018

a(n) = Sum_{k=1..n} tau(k^2)*floor(n/k).
Asymptotic to A*n*log(n)^3 + B*n*log(n)^2 + C*n*log(n) + D*n + O(n^(1/2+eps)) where A = 1/Pi^2 and B = (12*gamma-3)/Pi^2 - 36*zeta'(2)/Pi^4. [corrected by Vaclav Kotesovec, Aug 30 2018]
C = 36*gamma^2/Pi^2 - (288*z1/Pi^4 + 24/Pi^2)*gamma + (864*z1^2/Pi^6 + 72*z1/Pi^4 - 72/Pi^4*z2 + 6/Pi^2) - 24*g1/Pi^2 and D = 24*gamma^3/Pi^2 - (432*z1 /Pi^4+ 36/Pi^2)*gamma^2 + (3456*z1^2/Pi^6 + 288*(z1-z2)/Pi^4 + 24/Pi^2 - 72*g1/Pi^2)*gamma + g1*(288*z1/Pi^4 + 24/Pi^2)-10368*z1^3/Pi^8 - 864*z1^2/Pi^6 + 1728*z2*z1/Pi^6 + 72*(z2-z1)/Pi^4- 48*z3/Pi^4 + (12*g2-6)/Pi^2, where gamma is the Euler-Mascheroni constant A001620, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994, z3 = Zeta'''(2) = A201995 and g1, g2 are the Stieltjes constants, see A082633 and A086279. - Vaclav Kotesovec, Sep 10 2018
See Cully-Hugill & Trudgian, Theorem 2, for an explicit version of the asymptotic given above. - Charles R Greathouse IV, Nov 19 2019

Definition corrected by N. J. A. Sloane, May 25 2008

A353551 a(n) = Sum_{k=1..n} tau(k^3), where tau is the number of divisors function A000005.

Original entry on oeis.org

0, 1, 5, 9, 16, 20, 36, 40, 50, 57, 73, 77, 105, 109, 125, 141, 154, 158, 186, 190, 218, 234, 250, 254, 294, 301, 317, 327, 355, 359, 423, 427, 443, 459, 475, 491, 540, 544, 560, 576, 616, 620, 684, 688, 716, 744, 760, 764, 816, 823, 851, 867, 895, 899, 939, 955, 995

Offset: 0

Karl-Heinz Hofmann, May 07 2022

nonn

			  A048785(0) = 0
+ A048785(1) = 1
+ A048785(2) = 4
+ A048785(3) = 4
------------------
= A353551(3) = 9

Karl-Heinz Hofmann, Table of n, a(n) for n = 0..10000

Partial sums of A048785.

Cf. A000005, A006218, A061503 (squares).

a:= proc(n) option remember; `if`(n=0, 0, a(n-1)+numtheory[tau](n^3)) end:
seq(a(n), n=0..100);  # Alois P. Heinz, May 08 2022

Accumulate[Join[{0}, Table[DivisorSigma[0, k^3], {k, 1, 50}]]] (* Amiram Eldar, May 08 2022 *)

a(n) = sum(k=1, n, numdiv(k^3)); \\ Michel Marcus, May 08 2022

from sympy import divisor_count
def A048785(n): return divisor_count(n**3)
def A353551(n): return sum(A048785(n) for n in range(1, n))
print([A353551(n) for n in range(1, 58)])

from math import prod
from sympy import factorint
def A353551(n): return sum(prod(3*e+1 for e in factorint(k).values()) for k in range(1,n+1)) # Chai Wah Wu, May 10 2022

a(n) = Sum_{k=1..n} tau(k^3).

a(n) = a(n-1) + A048785(n) for n >= 1, a(0) = 0.

A182082 Number of pairs, (x,y), with x >= y, whose LCM does not exceed n.

Original entry on oeis.org

1, 3, 5, 8, 10, 15, 17, 21, 24, 29, 31, 39, 41, 46, 51, 56, 58, 66, 68, 76, 81, 86, 88, 99, 102, 107, 111, 119, 121, 135, 137, 143, 148, 153, 158, 171, 173, 178, 183, 194, 196, 210, 212, 220, 228, 233, 235, 249, 252, 260, 265, 273, 275, 286, 291, 302, 307, 312

Offset: 1

Walt Rorie-Baety, Apr 10 2012

nonn

Note that this is the asymmetric count. If all pairs (x,y) are counted, A061503 is obtained. - T. D. Noe, Apr 10 2012

			a(1000000) = 37429395, according to Project Euler problem #379.

Walt Rorie-Baety, Table of n, a(n) for n = 1..1000
Project Euler, Problem 379: Least common multiple count.

Partial sums of A018892.

Cf. A000005, A007875, A013661, A061503 (symmetric case).

a n = length [(x,y)| x <- [1..n], y <- [x..n], lcm x y <= n]

Table[Count[Flatten[Table[LCM[i, j], {i, n}, {j, i, n}]], ?(# <= n &)], {n, 60}] (* _T. D. Noe, Apr 10 2012 *)
nn = 100; (Accumulate[Table[DivisorSigma[0, n^2], {n, nn}]] + Range[nn])/2 (* T. D. Noe, Apr 10 2012 *)

a(n)=(sum(k=1,n,numdiv(k^2))+n)/2 \\ Charles R Greathouse IV, Apr 10 2012

a(n) = Sum_{k=1..n} (d(k^2)+1)/2, where d is the number of divisors function (A000005). - Charles R Greathouse IV, Apr 10 2012
a(n) = Sum_{k=1..n} A007875(k) * floor(n/k). - Daniel Suteu, Jan 08 2021
a(n) ~ n * log(n)^2 /(4*zeta(2)) (see A018892 for a more accurate asymptotic formula). - Amiram Eldar, Feb 01 2025

A306775 Partial sums of A060648: sum of the inverse Moebius transform of the Dedekind psi function from 1 to n.

Original entry on oeis.org

1, 5, 10, 20, 27, 47, 56, 78, 95, 123, 136, 186, 201, 237, 272, 318, 337, 405, 426, 496, 541, 593, 618, 728, 765, 825, 878, 968, 999, 1139, 1172, 1266, 1331, 1407, 1470, 1640, 1679, 1763, 1838, 1992, 2035, 2215, 2260, 2390, 2509, 2609, 2658, 2888, 2953, 3101

Offset: 1

Daniel Suteu, Mar 09 2019

nonn

In general, for m >= 1, Sum_{k=1..n} Sum_{d|k} psi_m(d) = Sum_{k=1..n} k^m * A064608(floor(n/k)), where psi_m(d) is the generalized Dedekind psi function.

Additionally, for m >= 1, Sum_{k=1..n} Sum_{d|k} psi_m(d) ~ (n^(m+1) * zeta(m+1)^2) / ((m+1) * zeta(2*(m+1))).

Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
Wikipedia, Dedekind psi function

Cf. A001221, A001615, A034444, A060648, A061503, A064608.

with(numtheory): psi := n -> n*mul(1+1/p, p in factorset(n)):
seq(add(psi(i)*floor(n/i), i=1..n), n=1..80); # Ridouane Oudra, Aug 27 2019

Accumulate[Table[Sum[EulerPhi[n/d] * DivisorSigma[0, d^2], {d, Divisors[n]}], {n, 1, 100}]] (* Vaclav Kotesovec, Oct 09 2019 *)

a(n) = sum(k=1, n, 2^omega(k) * (n\k) * (1+n\k))/2;

a(n) ~ (5/4) * n^2.
a(n) = Sum_{k=1..n} A060648(k).
a(n) = Sum_{k=1..n} Sum_{d|k} A001615(d).
a(n) = Sum_{k=1..n} k * A064608(floor(n/k)).
a(n) = (1/2)*Sum_{k=1..n} 2^omega(k) * floor(n/k) * floor(1+n/k).
a(n) = Sum_{k=1..n} A001615(k)*floor(n/k). - Ridouane Oudra, Aug 27 2019

cp's OEIS Frontend

A048691 a(n) = d(n^2), where d(k) = A000005(k) is the number of divisors of k.

Views

Author

Keywords

Comments

References

Links

Crossrefs

Programs

Haskell

Mathematica

MuPAD

PARI

PARI

Sage

Formula

Extensions

A060648 Number of cyclic subgroups of the group C_n X C_n (where C_n is the cyclic group of order n).

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Maple

Mathematica

PARI

Sage

Formula

Extensions

A061502 a(n) = Sum_{k<=n} tau(k)^2, where tau = number of divisors function A000005.

Views

Author

Keywords

References

Links

Crossrefs

Programs

Magma

Mathematica

PARI

PARI

PARI

Formula

Extensions

A353551 a(n) = Sum_{k=1..n} tau(k^3), where tau is the number of divisors function A000005.

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

Maple

Mathematica

PARI

Python

Python

Formula

A182082 Number of pairs, (x,y), with x >= y, whose LCM does not exceed n.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Haskell

Mathematica

PARI

Formula

A306775 Partial sums of A060648: sum of the inverse Moebius transform of the Dedekind psi function from 1 to n.

Views

Author

Keywords

Comments