A292905 Decimal expansion of Product_{k>=1} (1 - exp(-5*Pi*k)).

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

Offset

0,1

Links

Table of n, a(n) for n=0..105.

Eric Weisstein's World of Mathematics, Dedekind Eta Function

Eric Weisstein's World of Mathematics, q-Pochhammer Symbol

Wikipedia, Dedekind eta function

Wikipedia, Euler function

Formula

Equals exp(5*Pi/8) * Gamma(1/4) * (9 + 4*sqrt(5))^(1/4) * (-exp(5*Pi/2) + sqrt(exp(5*Pi) + 64*r^24))^(1/4) / (2^(7/4) * sqrt(5) * Pi^(3/4) * r^5), where r = A292904 = 1.00000015070175025002398949386987146797376100643050740569...

Equals exp(5*Pi/24) * Gamma(1/4) * (7 + 3*sqrt(5) + 12*sqrt(14*sqrt(5) - 30))^(1/8) / (2*sqrt(5)*Pi^(3/4)). - Vaclav Kotesovec, May 13 2023

Example

0.999999849298249749982855684249951337192226280495972174466518680326272...

Mathematica

RealDigits[QPochhammer[E^(-5*Pi)], 10, 120][[1]]
RealDigits[E^(5*Pi/8) * Gamma[1/4] * (9 + 4*Sqrt[5])^(1/4) * (-E^(5*Pi/2) + Sqrt[E^(5*Pi) + 64*r^24])^(1/4) / (2^(7/4) * Sqrt[5] * Pi^(3/4) * r^5)/.r -> (r/.FindRoot[2^(3/4)*r^6 + 2^(17/8)*E^(5*Pi/24)*r^5 + 2^(5/8)*E^(25*Pi/24)*r - E^(5*Pi/4) == 0, {r, 1}, WorkingPrecision -> 130]), 10, 120][[1]]
RealDigits[E^(5*Pi/24) * Gamma[1/4]*(7 + 3*Sqrt[5] + 12*Sqrt[14*Sqrt[5] - 30])^(1/8) / (2*Sqrt[5]*Pi^(3/4)), 10, 120][[1]] (* Vaclav Kotesovec, May 13 2023 *)

Crossrefs

Cf. A292862, A292863, A259147, A259148, A259149, A292888, A259150, A259151, A292864.

Cf. A292904.

Sequence in context: A091668 A196498 A277535 * A361352 A363018 A269351

Adjacent sequences: A292902 A292903 A292904 * A292906 A292907 A292908

Keyword

nonn,cons

Author

Vaclav Kotesovec, Sep 26 2017

Status

approved