A065480 -id:A065480 - cp's OEIS frontend

A065492 Exponents in expansion of constant A065480 as a product zeta(n)^(-a(n)).

0, 1, -1, 2, -4, 8, -14, 25, -48, 92, -168, 310, -590, 1117, -2092, 3945, -7500, 14264, -27102, 51627, -98694, 188934, -361936, 694565, -1335466, 2570965, -4954744, 9561045, -18473140, 35730392, -69176558, 134063535, -260062168, 504918960

Offset: 0

N. J. A. Sloane, Nov 19 2001

sign

Inverse Euler transform of A077925 shifted by two places: 1, 0, 1, -1, 3, -5,... [From R. J. Mathar, Jul 26 2010]

Vaclav Kotesovec, Table of n, a(n) for n = 0..3000
G. Niklasch, Some number theoretical constants: 1000-digit values [Cached copy]

Cf. A065480.

nmax = 40; s = {}; For[j = 1, j <= nmax, j++, AppendTo[s, j*(1 - (-2)^(j - 1))/3 - Sum[s[[d]]*(1 - (-2)^(j - d - 1))/3, {d, j - 1}]]]; Table[Sum[If[Divisible[j, d], MoebiusMu[j/d], 0]*s[[d]], {d, 1, j}]/j, {j, nmax}] (* Vaclav Kotesovec, Jun 13 2020 *)

a(n) ~ -(-1)^n * 2^(n+1) / n. - Vaclav Kotesovec, Jun 13 2020

More terms from R. J. Mathar, Jul 26 2010

A065463 Decimal expansion of Product_{p prime} (1 - 1/(p*(p+1))).

Original entry on oeis.org

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

Offset: 0

N. J. A. Sloane, Nov 19 2001

The density of A268335. - Vladimir Shevelev, Feb 01 2016

The probability that two numbers are coprime given that one of them is coprime to a randomly chosen third number. - Luke Palmer, Apr 27 2019

			0.7044422009991655927366033503...

Olivier Bordellès and Benoit Cloitre, An Alternating Sum Involving the Reciprocal of Certain Multiplicative Functions, J. Int. Seq., Vol. 16 (2013), Article 13.6.3.
Eckford Cohen, Arithmetical functions associated with the unitary divisors of an integer, Mathematische Zeitschrift, Vol. 74, No. 1 (1960), pp. 66-80.
Steven R. Finch, Mathematical Constants II, Encyclopedia of Mathematics and Its Applications, Cambridge University Press, Cambridge, 2018, p. 50.
David Handelman, Invariants for critical dimension groups and permutation-Hermite equivalence, arXiv preprint arXiv:1309.7417 [math.AC], 2013-2017.
R. J. Mathar, Hardy-Littlewood constants embedded into infinite products over all positive integers, arxiv:0903.2514 [math.NT] (2009) constant Q_1^(1).
G. Niklasch, Some number theoretical constants: 1000-digit values.
G. Niklasch, Some number theoretical constants: 1000-digit values. [Cached copy]
V. Sita Ramaiah and D. Suryanarayana, Sums of reciprocals of some multiplicative functions, Mathematical Journal of Okayama University, Vol. 21, No. 2 (1979), pp. 155-164.
R. Sitaramachandrarao and D. Suryanarayana, On Sigma_{n<=x} sigma*(n) and Sigma_{n<=x} phi*(n), Proceedings of the American Mathematical Society, Vol. 41, No. 1 (1973), pp. 61-66.
László Tóth, Alternating sums concerning multiplicative arithmetic functions, Journal of Integer Sequences, Vol. 20 (2017), Article 17.2.1,arXiv preprint, arXiv:1608.00795 [math.NT], 2016.
Deyu Zhang and Wenguang Zhai, Mean Values of a Gcd-Sum Function Over Regular Integers Modulo n, J. Int. Seq., Vol. 13 (2010), Article 10.4.7, eq. (4).
Rimer Zurita Generalized Alternating Sums of Multiplicative Arithmetic Functions, J. Int. Seq., Vol. 23 (2020), Article 20.10.4.

Cf. A001615, A007947, A047994, A078082, A268335, A306633.

Cf. A000203, A065473, A065480, A065490, A008683.

$MaxExtraPrecision = 1200; digits = 98; terms = 1200; P[n_] := PrimeZetaP[n]; LR = Join[{0, 0}, LinearRecurrence[{-2, 0, 1}, {-2, 3, -6}, terms + 10]]; r[n_Integer] := LR[[n]]; Exp[NSum[r[n]*P[n - 1]/(n - 1), {n, 3, terms}, NSumTerms -> terms, WorkingPrecision -> digits + 10]] // RealDigits[#, 10, digits]& // First (* Jean-François Alcover, Apr 18 2016 *)

prodeulerrat(1 - 1/(p*(p+1))) \\ Amiram Eldar, Mar 14 2021

From Amiram Eldar, Mar 05 2019: (Start)
Equals lim_{m->oo} (2/m^2)*Sum_{k=1..m} rad(k), where rad(k) = A007947(k) is the squarefree kernel of k (Cohen).
Equals lim_{m->oo} (2/m^2)*Sum_{k=1..m} uphi(k), where uphi(k) = A047994(k) is the unitary totient function (Sitaramachandrarao and Suryanarayana).
Equals lim_{m->oo} (1/log(m))*Sum_{k=1..m} 1/psi(k), where psi(k) = A001615(k) is the Dedekind psi function (Sita Ramaiah and Suryanarayana).
(End)
Equals A065473*A013661/A065480. - Luke Palmer, Apr 27 2019
Equals Sum_{k>=1} mu(k)/(k*sigma(k)), where mu is the Möbius function (A008683) and sigma(k) is the sum of divisors of k (A000203). - Amiram Eldar, Jan 14 2022
Equals 1/A065489. - R. J. Mathar, May 27 2025

A065464 Decimal expansion of Product_{p prime} (1 - (2*p-1)/p^3).

Original entry on oeis.org

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

Offset: 0

N. J. A. Sloane, Nov 19 2001

Sum_{n <= x} A189021(n) ~ kx, where k is this constant. - Charles R Greathouse IV, Jan 24 2018

The probability that a number chosen at random is squarefree and coprime to another randomly chosen random (see Schroeder, 2009). - Amiram Eldar, May 23 2020, corrected Aug 04 2020

			0.428249505677094440218765707581823546...

Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 2.5.1, p. 110.
Manfred Schroeder, Number Theory in Science and Communication, 5th edition, Springer, 2009, page 59.

R. J. Mathar, Hardy-Littlewood Constants Embedded into Infinite Products over All Positive Integers, arXiv:0903.2514 [math.NT], 2009-2011; Equation (116).
G. Niklasch, Some number theoretical constants: 1000-digit values. [Cached copy]
Eric Weisstein's World of Mathematics, Carefree Couple.

Cf. A000010, A057434, A078078, A056671.
Cf. A065463, A013661.
Cf. A065473, A065480.

$MaxExtraPrecision = 800; digits = 98; terms = 2000; LR = Join[{0, 0}, LinearRecurrence[{-2, 0, 1}, {-2, 3, -6}, terms+10]]; r[n_Integer] := LR[[n]]; (6/Pi^2)*Exp[NSum[r[n]*(PrimeZetaP[n-1]/(n-1)), {n, 3, terms}, NSumTerms -> terms, WorkingPrecision -> digits+10, Method -> "AlternatingSigns"]] // RealDigits[#, 10, digits]& // First (* Jean-François Alcover, Apr 16 2016 *)

prodeulerrat(1 - (2*p-1)/p^3) \\ Amiram Eldar, Mar 12 2021

Equals A065463 divided by A013661. - R. J. Mathar, Mar 22 2011
Equals A065473 divided by A065480. - R. J. Mathar, May 02 2019
Equals (6/Pi^2)^2 * Product_{p prime} (1 + 1/(p^3 + p^2 - p - 1)) = 1.1587609... * (6/Pi^2)^2. - Amiram Eldar, May 23 2020
Equals lim_{m->oo} (1/m) * Sum_{k==1..m} (phi(k)/k)^2, where phi is the Euler totient function (A000010). - Amiram Eldar, Mar 12 2021

More digits from Vaclav Kotesovec, Dec 18 2019

A078081 Continued fraction expansion of Product_{p prime} (1 - 1/(p^2+p-1)).

Original entry on oeis.org

0, 1, 2, 37, 1, 4, 23, 2, 15, 2, 1, 1, 1, 1, 1, 7, 4, 3, 2, 4, 1, 2, 1, 3, 1, 1, 1, 5, 1, 3, 2, 4, 1, 28, 2, 4, 7, 1, 1, 3, 23, 1, 5, 12, 8, 5, 1, 1, 1, 3, 1, 2, 3, 1, 2, 1, 27, 4, 3, 1, 1, 2, 1, 82, 2, 3, 10, 2, 3, 1, 2, 5, 2, 1, 1, 4, 6, 4, 1, 3, 1, 4, 18, 1, 2, 1, 2, 6, 2, 1, 1, 1, 2, 2, 5

Offset: 0

Benoit Cloitre, Dec 02 2002

Cf. A065480.

contfrac(prodeulerrat(1 - 1/(p^2+p-1))) \\ Amiram Eldar, Mar 14 2021

Offset changed by Andrew Howroyd, Jul 02 2024

A319597 Number of conjugacy classes for a non-abelian group of order p^3, where p is prime: a(n) = p^2 + p - 1 where p = prime(n).

Original entry on oeis.org

5, 11, 29, 55, 131, 181, 305, 379, 551, 869, 991, 1405, 1721, 1891, 2255, 2861, 3539, 3781, 4555, 5111, 5401, 6319, 6971, 8009, 9505, 10301, 10711, 11555, 11989, 12881, 16255, 17291, 18905, 19459, 22349, 22951, 24805, 26731, 28055, 30101, 32219, 32941, 36671

Offset: 1

Juan Lanfranco, Sep 23 2018

nonn

For a non-abelian group of order p^3, we can use the class equation, p-group has nontrivial center result, group modulo center is cyclic implies group is abelian result, and the orbit-stabilizer theorem to give the number of conjugacy classes and number of elements in each conjugacy class.

The elements of A028387 with prime index.

			For p^3=2^3=8, the conjugacy classes of the Dihedral group = <r, s | r^4=1, s^2=1, srs=r^{-1}> are {1}, {r^2}, {r, r^3}, {s, sr^2}, {sr, sr^3}.

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

Cf. A000040, A028387, A065480, A065489.

A028387:= n -> n^2+n-1:
seq(A028387(ithprime(i)),i=1..50); # Robert Israel, Dec 23 2018

f[n_]:=n^2 + n - 1 ; f[Prime[Range[43]]] (* Amiram Eldar, Nov 21 2018 *)

a(n) = {my(p = prime(n)); p^2 + p - 1; } \\ Amiram Eldar, Nov 07 2022

From Amiram Eldar, Nov 07 2022: (Start)
a(n) = A028387(A000040(n)-1).
Product_{n>=1} (1 + 1/a(n)) = A065489.
Product_{n>=1} (1 - 1/a(n)) = A065480. (End)

cp's OEIS Frontend

A065492 Exponents in expansion of constant A065480 as a product zeta(n)^(-a(n)).

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A065463 Decimal expansion of Product_{p prime} (1 - 1/(p*(p+1))).

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A065464 Decimal expansion of Product_{p prime} (1 - (2*p-1)/p^3).

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A078081 Continued fraction expansion of Product_{p prime} (1 - 1/(p^2+p-1)).

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PARI

Extensions

A319597 Number of conjugacy classes for a non-abelian group of order p^3, where p is prime: a(n) = p^2 + p - 1 where p = prime(n).

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