A201994 -id:A201994 - cp's OEIS frontend

A208133 Total number of subgroups of rank <= 2 of a certain class of abelian groups of order n defined as direct products of Z/(mZ) X Z/(kZ) with m|k.

1, 2, 2, 8, 2, 4, 2, 12, 9, 4, 2, 16, 2, 4, 4, 31, 2, 18, 2, 16, 4, 4, 2, 24, 11, 4, 14, 16, 2, 8, 2, 42, 4, 4, 4, 72, 2, 4, 4, 24, 2, 8, 2, 16, 18, 4, 2, 62, 13, 22, 4, 16, 2, 28, 4, 24, 4, 4, 2, 32, 2, 4, 18, 90, 4, 8, 2, 16, 4, 8, 2, 108, 2, 4, 22, 16

Offset: 1

R. J. Mathar, Mar 29 2012

Level function l_tau^2(n) of Bhowmik and Wu.

Records occur at 1, 2, 4, 8, 12, 16, 32, 36, 64, 72, 108, 128, 144, 288, 432, 576, 1152, 1296, 2304, 3600, 5184, 7200, 9216, 10368, 14112, 14400, 20736, 28224, 28800, 32400, 57600, ... and they are: 1, 2, 8, 12, 16, 31, 42, 72, 90, 108, 112, 116, 279, 378, 434, 810, 1044, 1302, 2025, 3069, 3780, 4158, 4644, 4872, 4914, 8910, 9450, 10530, 11484, 14322, 22275, ... - Antti Karttunen, Mar 21 2018

A. Laurincikas, The universality of Dirichlet series attached to finite Abelian groups, in "Number Theory", Proc. Turku Sympos. on Number Theory, May 31-June 4, 1999, p 179.

Antti Karttunen, Table of n, a(n) for n = 1..65537
G. Bhowmik, Jie Wu, Zeta function of subgroups of abelian groups and average orders, J. reine angew. Math. 530 (2001) 1-15.
Vaclav Kotesovec, Graph - the asymptotic ratio (1000000 terms)

Cf. A010052, A037213, A300828.

L300828 := [ 1, 0, 0, 1, 0, 0, 0, -2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, -2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0
] ;
L010052 := [ 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ];
L037213 := [ 1, 0, 0, 2, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ] ;
Lx := DIRICHLET(L300828,L037213) ;
Lx := DIRICHLET(Lx,L010052) ;
Lx := DIRICHLET(Lx,L010052) ;
Lx := MOBIUSi(Lx) ;
Lx := MOBIUSi(Lx) ;
# Name of initial list L1 changed to L300828 to refer to sequence A300828 by Antti Karttunen, Mar 21 2018

A037213(n) = if(issquare(n),sqrtint(n),0);
A300828(n) = { if(1==n, return(1)); my(val=1, v=factor(n), d=matsize(v)[1]); for(i=1,d, if(v[i,2] < 2 || v[i,2] > 3, return(0)); if (v[i,2] == 3, val *= -2)); return(val); };
a208133s1(n) = sumdiv(n,d,A037213(n/d)*A300828(d));
a208133s2(n) = sumdiv(n,d,issquare(n/d)*a208133s1(d));
a208133s3(n) = sumdiv(n,d,issquare(n/d)*a208133s2(d));
a208133s4(n) = sumdiv(n,d,a208133s3(d));
A208133(n) = sumdiv(n,d,a208133s4(d)); \\ Antti Karttunen, Mar 21 2018, after R. J. Mathar's Maple code

for(n=1, 100, print1(direuler(p=2, n, (1 + X + 2*X^2)/(1 - X)^3/(1 + X)^2/(1 - p*X^2))[n], ", ")) \\ Vaclav Kotesovec, Jun 18 2020

Dirichlet g.f.: zeta(s)^2*zeta(2s)^2*zeta(2s-1)*Product_{primes p} (1 + 1/p^(2s) - 2/p^(3s)).
Sum_{k=1..n} a(k) ~ c * Pi^4 * log(n)^2 * n / 144, where c = A330594 = Product_{primes p} (1 + 1/p^2 - 2/p^3) = 1.10696011195321767665117913000743959294954883365812241904313404497877733241... - Vaclav Kotesovec, Dec 18 2019
More precise asymptotics: Let f(s) = Product_{primes p} (1 + 1/p^(2*s) - 2/p^(3*s)), then Sum_{k=1..n} a(k) ~ n*Pi^2 * (Pi^2 * f(1) * log(n)^2 + 2*Pi^2 * log(n) * (f(1) * (-1 + 8*gamma - 48*log(A) + 4*log(2*Pi)) + f'(1)) + Pi^2 * (2*f(1)*(1 + 25*gamma^2 + 576*log(A)^2 + log(A) * (48 - 96*log(2*Pi)) - 8*gamma * (1 + 36*log(A) - 3*log(2*Pi)) - 4*log(2*Pi) + 4*log(2*Pi)^2 - 6*sg1) + 2*(-1 + 8*gamma - 48*log(A) + 4*log(2*Pi))*f'(1) + f''(1)) + 48*f(1)*zeta''(2)) / 144, where f(1) = A330594, f'(1) = A330594 * (-A335705) = f(1) * Sum_{primes p} = -2*(p-3) * log(p) / (p^3 + p - 2) = -0.087825458097278818094375273108270679512035928574..., f''(1) = A330594 * (A335705^2 + A335706) = f'(1)^2/f(1) + f(1) * Sum_{primes p} = 2*p*(2*p^3 - 9*p^2 - 1) * log(p)^2) / (p^3 + p - 2)^2 =  0.26722508718782634450711076996710402451611235402675360769..., zeta''(2) = A201994, A is the Glaisher-Kinkelin constant A074962, gamma is the Euler-Mascheroni constant A001620 and sg1 is the first Stieltjes constant (see A082633). - Vaclav Kotesovec, Jun 18 2020

A092089 Number of odd-length palindromes among the k-tuples of partial quotients of the continued fraction expansions of n/r, r = 1, ..., n.

Original entry on oeis.org

1, 2, 3, 4, 3, 6, 3, 8, 5, 6, 3, 12, 3, 6, 9, 12, 3, 10, 3, 12, 9, 6, 3, 24, 5, 6, 7, 12, 3, 18, 3, 16, 9, 6, 9, 20, 3, 6, 9, 24, 3, 18, 3, 12, 15, 6, 3, 36, 5, 10, 9, 12, 3, 14, 9, 24, 9, 6, 3, 36, 3, 6, 15, 20, 9, 18, 3, 12, 9, 18, 3, 40, 3, 6, 15, 12, 9, 18, 3, 36, 9, 6, 3, 36, 9, 6, 9, 24, 3

Offset: 1

John W. Layman, Mar 29 2004

Suggested by R. K. Guy, Mar 26 2004
From Jianing Song, Mar 24 2019: (Start)
a(n) is also the number of inequivalent residue classes modulo n where the equivalence relation is defined as [a] ~ [b] (mod n) if and only if there exists some k such that gcd(k, n) = 1 and that a*k^2 == b (mod n). For example, for n = 16, the inequivalent residue classes are {[0], [1], [2], [3], [4], [5], [6], [7], [8], [10], [12], [14]}, so a(16) = 14.
Proof: let S(n) be the set of inequivalent residue classes modulo n, so our goal is to show that |S(n)| = a(n) for all n. By the Chinese Remainder Theorem, if gcd(s, t) = 1, then [a] ~ [b] (mod s*t) if and only if [a] ~ [b] (mod s) and [a] ~ [b] (mod t), so there is a one-to-one correspondence between S(s*t) and S(s) X S(t), that is, |S(n)| is multiplicative. It is obvious that |S(p^e)| = a(p^e), so |S(n)| = a(n) for all n. (End)

			[1, 2, 1, 2, 1] <-> 1+1/(2+1/(1+1/(2+1/1))) = 15/11 is one of the nine palindromes {[15], [5], [3, 1, 3], [3], [1, 1, 1], [1, 2, 1, 2, 1], [1, 3, 1], [1, 13, 1], [1]} among the continued fraction expansions of 15/r for r = 1..15. Thus a(15)=9.

Antti Karttunen, Table of n, a(n) for n = 1..10000
Agustina Czenky, Diagramatics for cyclic pointed fusion categories, arXiv:2404.08084 [math.QA], 2024. See p. 15.
László Tóth, Menon's identity and arithmetical sums representing functions of several variables, Rend. Sem. Mat. Univ. Politec. Torino, 69 (2011), 97-110 (see (37) in Corollary 15, p. 108).
Eric Weisstein's World of Mathematics, Partial quotient.

Cf. A001620, A201994, A306016.

Table[Apply[Times, FactorInteger[n] /. {p_, e_} /; p > 0 :> Which[p == 1, 1, OddQ@ p, 2 e + 1, And[p == 2, e == 1], 2, True, 4 (e - 1)]], {n, 89}] (* Michael De Vlieger, Sep 11 2017 *)

a(n) = if (n % 2, numdiv(n^2), if (n/2 % 2, 2*numdiv((n/2)^2), val = valuation(n, 2); 4*(val-1)*numdiv((n/2^val)^2))); \\ Michel Marcus, Jun 26 2014

(define (A092089 n) (cond ((= 1 n) n) ((zero? (modulo n 4)) (* 4 (+ -1 (A067029 n)) (A092089 (A000265 n)))) ((even? n) (* 2 (A092089 (/ n 2)))) (else (* (+ 1 (* 2 (A067029 n))) (A092089 (A028234 n)))))) ;; Antti Karttunen, Sep 11 2017

Conjecture: Let n = (2^k0)*(p1^k1)*(p2^k2)*...*(pm^km) be the prime factorization of n where p1, p2, ..., pm are distinct primes. Then a(n) is multiplicative and is given by a(n) = f(k0)*g(k1)*g(k2)*...*g(km), where f(0) = 1, f(1) = 2, f(k) = 4(k-1) if k>1 and g(k) = 2k+1 (This has been verified for n = 1-10000.) [Corrected by Jianing Song, Mar 24 2019]
Multiplicative with a(p^e) = 2e+1 if p is odd; a(2) = 2, a(2^e)= 4*(e-1), if e > 1. - Michel Marcus, Jun 26 2014
Dirichlet g.f.: zeta(s)^3/zeta(2*s) * (1 - 1/2^s + 1/2^(2*s-1)). - Jianing Song, Mar 25 2019 [corrected by Amiram Eldar, Dec 18 2023]
Sum_{k=1..n} a(k) ~ (3/Pi^2) * n * (log(n^2) + c_1 * log(n) + c_2), where c_1 = 6 * gamma - 2 - log(2) - 4*zeta'(2)/zeta(2) = 3.04999078122..., gamma is Euler's constant (A001620), c_2 = 2 - 6 * gamma + 6 * gamma^2 + log(2) - 3 * gamma * log(2) + 3*log(2)^2/2 - 6 *gamma_1 + 4*zeta'(2)/zeta(2) + (2 * log(2) - 12 * gamma) * zeta'(2)/zeta(2) + 8 * (zeta'(2)/zeta(2))^2 - 4 * zeta''(2)/zeta(2) = -0.1743888255..., and gamma_1 is the 1st Stieltjes constant (A082633). - Amiram Eldar, Dec 18 2023

A102887 Decimal expansion of Integral_{x=0..1} log(gamma(x))^2 dx.

Original entry on oeis.org

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

Offset: 1

Eric W. Weisstein, Jan 15 2005

Also equals (1/6)*log(2*Pi)^2 + 2*log(A)*log(2*Pi) - (1/6)*gamma*log(2*Pi) + Pi^2/48 + 2*gamma*log(A) + zeta''(2)/(2*Pi^2) (with A the Glaisher-Kinkelin constant). - Jean-François Alcover, Apr 29 2013

			1.8663170837935620809929679379782897398...

George Boros and Victor H. Moll, Irresistible integrals, Cambridge University Press (2006), p. 236.

G. C. Greubel, Table of n, a(n) for n = 1..10000
M. L. Glasser, A note on Beukers's and related integrals, Amer. Math. Monthly 126(4) (2019), 361-363.

Cf. A001620, A074962, A075700, A201994.

EulerGamma^2/12 + Pi^2/48 + (EulerGamma*Log[2*Pi])/6 + Log[2*Pi]^2/3 - ((EulerGamma + Log[2*Pi])*Zeta'[2])/Pi^2 + Zeta''[2]/(2*Pi^2)

intnum(x=0,1, log(gamma(x))^2) \\ Michel Marcus, Aug 27 2015

Equals gamma^2/12 + Pi^2/48 + (gamma*log(2*Pi))/6 + log(2*Pi)^2/3 - ((gamma + log(2*Pi))*zeta'(2))/Pi^2 + zeta''(2)/(2*Pi^2).

Equals -Integral_{x=0..1, y=0..1} log(gamma(x*y))^2/log(x*y) dx dy. (Apply Theorem 1 or Theorem 2 in Glasser (2019).) - Petros Hadjicostas, Jun 30 2020

A174466 a(n) = Sum_{d|n} dsigma(n/d)tau(d).

Original entry on oeis.org

1, 7, 10, 31, 16, 70, 22, 111, 64, 112, 34, 310, 40, 154, 160, 351, 52, 448, 58, 496, 220, 238, 70, 1110, 166, 280, 334, 682, 88, 1120, 94, 1023, 340, 364, 352, 1984, 112, 406, 400, 1776, 124, 1540, 130, 1054, 1024, 490, 142, 3510, 316, 1162, 520, 1240

Offset: 1

Paul D. Hanna, Apr 04 2010

Compare to sigma_2(n) = Sum_{d|n} d*sigma(n/d)*phi(d) = sum of squares of divisors of n.
tau(n) = A000005(n) = the number of divisors of n,
and sigma(n) = A000203(n) = sum of divisors of n.
Dirichlet convolution of A038040 and A000203. - R. J. Mathar, Feb 06 2011

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

Cf. A000005 (tau), A000203 (sigma), A007425 (tau_3), A034718, A038040, A174465.

a174466 n = sum $ zipWith3 (((*) .) . (*))
                  divs (map a000203 $ reverse divs) (map a000005 divs)
                  where divs = a027750_row n
-- Reinhard Zumkeller, Jan 21 2014

[&+[d*DivisorSigma(1, n div d)*#Divisors(d):d in Divisors(n)]:n in [1..55]]; // Marius A. Burtea, Oct 18 2019

f[p_, e_] := ((e^2+3*e+2)*p^(e+3) - 2*(e^2+4*e+3)*p^(e+2) + (e^2+5*e+6)*p^(e+1) - 2)/(2*(p-1)^3); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, May 26 2025 *)

{a(n)=sumdiv(n,d,d*sigma(n/d)*sigma(d,0))}

Logarithmic derivative of A174465.
Dirichlet g.f.: zeta(s)*(zeta(s-1))^3. - R. J. Mathar, Feb 06 2011
a(n) = Sum_{d|n} tau_3(d)*d = Sum_{d|n} A007425(d)*d. - Enrique Pérez Herrero, Jan 17 2013
G.f.: Sum_{k>=1} k*tau_3(k)*x^k/(1 - x^k). - Ilya Gutkovskiy, Sep 06 2018
Sum_{k=1..n} a(k) ~ Pi^2*n^2/24 * (log(n)^2 + ((6*g - 1) + 12*z1/Pi^2) * log(n) + (1 - 6*g + 12*g^2 - 12*sg1)/2 + 6*((6*g - 1)*z1 + z2)/Pi^2), where g is the Euler-Mascheroni constant A001620, sg1 is the first Stieltjes constant A082633, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994. - Vaclav Kotesovec, Feb 02 2019
Multiplicative with a(p^e) = ((e^2+3*e+2)*p^(e+3) - 2*(e^2+4*e+3)*p^(e+2) + (e^2+5*e+6)*p^(e+1) - 2)/(2*(p-1)^3). - Amiram Eldar, May 26 2025

A257549 Decimal expansion of zeta''(0) (negated).

Original entry on oeis.org

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

Offset: 1

Jean-François Alcover, Apr 29 2015

Essentially the same as A245273. - R. J. Mathar, Apr 30 2015

			2.00635645590858485121010002672996043819899491016091988116986828...

Tom M. Apostol, Formulas for higher derivatives of the Riemann zeta function, Mathematics of Computation 44 (1985), p. 223-232.
Richard E. Crandall, Unified algorithms for polylogarithm, L-series, and zeta variants. p. 15.
Steven R. Finch, Mathematical Constants II, Encyclopedia of Mathematics and Its Applications, Cambridge University Press, Cambridge, 2018, p. 104.
Eric Weisstein's World of Mathematics, Riemann Zeta Function.
Eric Weisstein's World of Mathematics, Stieltjes Constants.

Cf. A075700, A082633, A261508, A201994.

evalf(-Zeta(2, 0), 120); # Vaclav Kotesovec, Apr 29 2015

RealDigits[ StieltjesGamma[1] + EulerGamma^2/2 - Pi^2/24 - (1/2)*(Log[2] + Log[Pi])^2, 10, 104] // First

-zeta''(0) \\ Charles R Greathouse IV, Mar 10 2016

zeta''(0) = gamma_1 + gamma^2/2 - Pi^2/24 - (1/2)*(log(2)+log(Pi))^2, where gamma_1 is the first Stieltjes constant.

A319090 Decimal expansion of C, the coefficient of n*log(n) in the asymptotic formula of Ramanujan for Sum_{k=1..n} (d(k)^2), where d(k) is the number of distinct divisors of k.

Original entry on oeis.org

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

Offset: 0

Vaclav Kotesovec, Sep 10 2018

			0.823265208269485020156816453947090406301273270321142250892524579208530395971755...

Ramanujan's Papers, Some formulas in the analytic theory of numbers Messenger of Mathematics, XLV, 1916, 81-84, Formula (3).

Cf. A061502, A092742, A245074, A319091.

36*EulerGamma^2/Pi^2 - (288*Zeta'[2]/Pi^4 + 24/Pi^2)*EulerGamma + (864*Zeta'[2]^2/Pi^6 + 72*Zeta'[2]/Pi^4 - 72/Pi^4*Zeta''[2] + 6/Pi^2) - 24*StieltjesGamma[1]/Pi^2

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, where gamma is the Euler-Mascheroni constant A001620, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994 and g1 is the first Stieltjes constant, see A082633.

A319091 Decimal expansion of D, the coefficient of n in the asymptotic formula of Ramanujan for Sum_{k=1..n} (d(k)^2), where d(k) is the number of distinct divisors of k.

Original entry on oeis.org

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

Offset: 0

Vaclav Kotesovec, Sep 10 2018

			0.4603233722587214303937620863844189747632149035387392240584250348445902629324...

Ramanujan's Papers, Some formulas in the analytic theory of numbers Messenger of Mathematics, XLV, 1916, 81-84, Formula (3).

Cf. A061502, A092742, A245074, A319090.

24*EulerGamma^3/Pi^2 - (432*Zeta'[2] /Pi^4+ 36/Pi^2)*EulerGamma^2 + (3456*Zeta'[2]^2/Pi^6 + 288*(Zeta'[2]-Zeta''[2])/Pi^4 + 24/Pi^2 - 72*StieltjesGamma[1]/Pi^2)*EulerGamma + StieltjesGamma[1]*(288*Zeta'[2]/Pi^4 + 24/Pi^2)-10368*Zeta'[2]^3/Pi^8 - 864*Zeta'[2]^2/Pi^6 + 1728*Zeta''[2] * Zeta'[2]/Pi^6 + 72*(Zeta''[2]-Zeta'[2])/Pi^4 - 48*Zeta'''[2]/Pi^4 + (12*StieltjesGamma[2] - 6)/Pi^2

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.

A320896 a(n) = Sum_{k=1..n} k * tau(k)^2, where tau is A000005.

Original entry on oeis.org

1, 9, 21, 57, 77, 173, 201, 329, 410, 570, 614, 1046, 1098, 1322, 1562, 1962, 2030, 2678, 2754, 3474, 3810, 4162, 4254, 5790, 6015, 6431, 6863, 7871, 7987, 9907, 10031, 11183, 11711, 12255, 12815, 15731, 15879, 16487, 17111, 19671, 19835, 22523, 22695, 24279

Offset: 1

Vaclav Kotesovec, Oct 23 2018

nonn

Amiram Eldar, Table of n, a(n) for n = 1..10000
Ramanujan's Papers, Some formulas in the analytic theory of numbers, Messenger of Mathematics, XLV, 1916, 81-84.

Cf. A061502, A318755, A320897.

Cf. A000005, A006218, A143127, A319085, A320895.

Accumulate[Table[k*DivisorSigma[0, k]^2, {k, 1, 50}]]

a(n) = sum(k=1, n, k*numdiv(k)^2); \\ Michel Marcus, Oct 23 2018

a(n) ~ n^2 * (3*(Pi^6*(-1 - 24*g^2 + 32*g^3 + g*(8 - 96*s1) + 16*s1 + 16*s2) - 13824*z1^3 + 576*Pi^2*z1*((-1 + 8*g)*z1 + 4*z2) - 8*Pi^4*(3*(1 - 8*g + 24*g^2 - 16*s1)*z1 - 6*z2 + 48*g*z2 + 8*z3)) + 6*(Pi^6*(1 - 8*g + 24*g^2 - 16*s1) + 576*Pi^2*z1^2 - 24*Pi^4*(-z1 + 8*g*z1 + 2*z2))*log(n) + 6*((-1 + 8*g)*Pi^6 - 24*Pi^4*z1)*log(n)^2 + 4*Pi^6*log(n)^3) / (8*Pi^8), where g is the Euler-Mascheroni constant A001620, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994, z3 = Zeta'''(2) = A201995 and s1, s2 are the Stieltjes constants, see A082633 and A086279.

A320897 a(n) = Sum_{k=1..n} k^2 * tau(k)^2, where tau is A000005.

Original entry on oeis.org

1, 17, 53, 197, 297, 873, 1069, 2093, 2822, 4422, 4906, 10090, 10766, 13902, 17502, 23902, 25058, 36722, 38166, 52566, 59622, 67366, 69482, 106346, 111971, 122787, 134451, 162675, 166039, 223639, 227483, 264347, 281771, 300267, 319867, 424843, 430319, 453423

Offset: 1

Vaclav Kotesovec, Oct 23 2018

nonn

In general, for m>=0, Sum_{k=1..n} k^m * tau(k)^2 ~ n^(m+1) * (log(n))^3 / ((m+1) * Pi^2).

Amiram Eldar, Table of n, a(n) for n = 1..10000
Ramanujan's Papers, Some formulas in the analytic theory of numbers, Messenger of Mathematics, XLV, 1916, 81-84.

Cf. A061502, A318755, A320896.

Cf. A000005, A006218, A143127, A319085, A320895.

Accumulate[Table[k^2*DivisorSigma[0, k]^2, {k, 1, 50}]]

a(n) = sum(k=1, n, k^2*numdiv(k)^2); \\ Michel Marcus, Oct 23 2018

a(n) ~ n^3 * (2*Pi^6*(-1 + 12*g - 54*g^2 + 108*g^3 + 36*s1 - 324*g*s1 + 54*s2) - 93312*z1^3 + 2592*Pi^2*z1*(-z1 + 12*g*z1 + 6*z2) - 72*Pi^4*(z1 - 12*g*z1 + 54*g^2*z1 - 36*s1*z1 - 3*z2 + 36*g*z2 + 6*z3) + 6*(Pi^6*(1 - 12*g + 54*g^2 - 36*s1) + 1296*Pi^2*z1^2 - 36*Pi^4*(-z1 + 12*g*z1 + 3*z2))*log(n) + 9*((-1 + 12*g)*Pi^6 - 36*Pi^4*z1)*log(n)^2 + 9*Pi^6*log(n)^3) / (27*Pi^8), where g is the Euler-Mascheroni constant A001620, z1 = Zeta'(2) = A073002, z2 = Zeta''(2) = A201994, z3 = Zeta'''(2) = A201995 and s1, s2 are the Stieltjes constants, see A082633 and A086279.

A340442 Decimal expansion of zeta''(3), the second derivative of the Riemann zeta function at 3.

Original entry on oeis.org

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

Offset: 0

R. J. Mathar, Jan 07 2021

			0.239746917305387184244176549838881...

Cf. A201994, A340443.

Maple
```
evalf(Zeta(2,3.0),100) ;
```

RealDigits[Zeta''[3], 10, 100][[1]] (* Amiram Eldar, May 28 2021 *)

PARI
```
zeta''(3) \\ Michel Marcus, Jan 07 2021
```

Equals Sum_{k>=1} log(k)^2/k^3. - Amiram Eldar, May 28 2021

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A174466 a(n) = Sum_{d|n} dsigma(n/d)tau(d).