A268046 -id:A268046 - cp's OEIS frontend

A339135 Decimal expansion of J = 2log(2)/3 - Re(Psi(1/2 + isqrt(3)/2)), where Psi is the digamma function and i=sqrt(-1).

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

Offset: 0

Artur Jasinski, Nov 25 2020

Generally in the literature there is no explicit formula for the real part of the function Psi(x + i*y) when y != 0.

Up to now there is no explicit formula expressing the constant J in terms of other mathematical constants.

			J = 0.677024679102993347...

Cf. A097663, A097663-A097676, A268046, A268086, A257958, A257959, A338815, A339237.

evalf(1 + 2*log(2)/3 - Psi(0, 5/2 - sqrt(3)*I/2)/2 - Psi(0, 5/2 + sqrt(3)*I/2)/2, 100); # Vaclav Kotesovec, Nov 26 2020

RealDigits[N[Re[2 Log[2]/3 - PolyGamma[0, 1/2 + I Sqrt[3]/2]], 110]][[1]]
Chop[N[1 + 2*Log[2]/3 - PolyGamma[0, 5/2 - I*Sqrt[3]/2]/2 - PolyGamma[0, 5/2 + I*Sqrt[3]/2]/2, 120]] (* Vaclav Kotesovec, Nov 26 2020 *)

2*log(2)/3 - real(psi(1/2 + I*sqrt(3)/2)) \\ Michel Marcus, Nov 25 2020

J = -log(2)/3 - (1/2)*Pi/cosh(Pi*sqrt(3)/2) - Re(Psi(1/4 + i*sqrt(3)/4)).
J = -log(2)/3 + (1/2)*Pi/cosh(Pi*sqrt(3)/2) - Re(Psi(3/4 + i*sqrt(3)/4)).
J = 3 + gamma + (2/3)*log(2) - (1/2)* sqrt(3)*Pi*tanh(Pi*sqrt(3)/2) - 3*(Sum_{n>=1} zeta(3*n)-1), where zeta is Riemann zeta function and gamma is Euler gamma constant see A001620.
J = -(1/2) + gamma + (2/3)*log(2) + (3/2)*(Sum_{n>=1} zeta(3*n+1)-1).
J = -1 + gamma + (2/3)*log(2) + (1/2)*sqrt(3)*Pi*tanh(Pi*sqrt(3)/2) - 3*(Sum_{n>=0} zeta(3*n+2)-1).
J = -(3/8) + gamma + (2/3)*log(2) + (3/2)*(Sum_{n>=1} zeta(6*n+1)-1).
J = 1/4 + gamma + (2/3)*log(2) - 3*(Sum_{n>=0} zeta(6*n+3)-1).
J = -(1/4) + gamma + (2/3)*log(2) - 3 (Sum_{n>=0} zeta(6*n+5)-1).
J = (11/12 - (1/4)*i*sqrt(3))*Psi(1/2 + i*sqrt(3)/2) + (-(5/4) + (1/4)*i*sqrt(3))*Psi(-(1/2) - i*sqrt(3)/2) + (-(17/24) + (1/8)*i*sqrt(3))* Psi(1/4 + i*sqrt(3)/4) + (3/8 - (1/8)*i*sqrt(3))*Psi(-(1/4) - i*sqrt(3)/4) + (-(17/24) + (1/8)*i*sqrt(3))*Psi(3/4 + i*sqrt(3)/4) + (3/8 - (1/8)*i*sqrt(3))*Psi(-(3/4) - i*sqrt(3)/4).
J = 2*log(2)/3 - Integral_{t=0..infinity} cosh(t)/t - sinh(t)/t - (cos(sqrt(3)*t)*cosh(t/2))/(1 - cosh(t) + sinh(t)) + (cos(sqrt(3)*t)*sinh(t/2))/(1 - cosh(t) + sinh(t)).
J = gamma + (1/6)*Sum_{t>=1} (6*t^3-4*t^2-4*t-1)/(t*(t+1)*(2t+1)*(t^2+t+1)).
Equals 1 + 2*log(2)/3 - Psi(0, 5/2 - i*sqrt(3)/2)/2 - Psi(0, 5/2 + i*sqrt(3)/2)/2. - Vaclav Kotesovec, Nov 26 2020

A268086 Decimal expansion of Sum_{k>0} 1/(k*((k+1)^2+1)).

Original entry on oeis.org

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

Offset: 0

Bruno Berselli, Jan 26 2016

Also, decimal expansion of Integral_{x=0..1} (2 - (1-i)*x^(1-i) - (1+i)*x^(1+i))/(4 - 4*x) dx, where i is the imaginary unit.

			.297595969027714331872169889027156331536383020649824278231847237306809...

Cf. A062158: numbers of the form k*((k+1)^2+1), with k>-2.

Cf. A268046: (1+i)*(H(1-i)-i*H(1+i))/4.

((1-I)*(harmonic(1-I) + I*harmonic(1+I)))/4:
Re(evalf(%, 106)); # Peter Luschny, Jan 27 2016

(1 - I)*(HarmonicNumber[1 - I] + I*HarmonicNumber[1 + I])/4 // Re // RealDigits[#, 10, 100]& // First (* Jean-François Alcover, Jan 26 2016 *)

# Warning: Floating point calculation. Adjust precision as needed
# and use some guard digits!
from mpmath import mp, chop, psi, coth, pi
mp.dps = 108; mp.pretty = True
chop((psi(0,I-1)-psi(0,1)-I+1)/2-pi*(I+1)*coth(pi)/4) # Peter Luschny, Jan 27 2016

Equals (1 - i)*(H(1-i) + i*H(1+i))/4, where H(z) is a harmonic number with complex argument.

Equals (Psi(i-1)-Psi(1)-i+1)/2 - Pi*(i+1)*coth(Pi)/4, where Psi(x) is the digamma function. - Peter Luschny, Jan 27 2016

cp's OEIS Frontend

A339135 Decimal expansion of J = 2log(2)/3 - Re(Psi(1/2 + isqrt(3)/2)), where Psi is the digamma function and i=sqrt(-1).

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A268086 Decimal expansion of Sum_{k>0} 1/(k*((k+1)^2+1)).

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cp's OEIS Frontend

A339135 Decimal expansion of J = 2*log(2)/3 - Re(Psi(1/2 + i*sqrt(3)/2)), where Psi is the digamma function and i=sqrt(-1).

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A268086 Decimal expansion of Sum_{k>0} 1/(k*((k+1)^2+1)).

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A339135 Decimal expansion of J = 2log(2)/3 - Re(Psi(1/2 + isqrt(3)/2)), where Psi is the digamma function and i=sqrt(-1).