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A153071 Decimal expansion of L(3, chi4), where L(s, chi4) is the Dirichlet L-function for the non-principal character modulo 4. 21
9, 6, 8, 9, 4, 6, 1, 4, 6, 2, 5, 9, 3, 6, 9, 3, 8, 0, 4, 8, 3, 6, 3, 4, 8, 4, 5, 8, 4, 6, 9, 1, 8, 6, 0, 0, 0, 6, 9, 5, 4, 0, 2, 6, 7, 6, 8, 3, 9, 0, 9, 6, 1, 5, 4, 4, 2, 0, 1, 6, 8, 1, 5, 7, 4, 3, 9, 4, 9, 8, 4, 1, 1, 7, 0, 8, 0, 3, 3, 1, 3, 6, 7, 3, 9, 5, 9, 4, 0, 7 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

Leonhard Euler, Introductio in Analysin Infinitorum, First Part, Articles 175, 284 and 287.

Bruce C. Berndt, Ramanujan's Notebooks, Part II, Springer-Verlag, 1989. See page 293, Entry 25 (iii).

LINKS

Table of n, a(n) for n=0..89.

Qing-Hu Hou, Zhi-Wei Sun, A q-analogue of the identity Sum_{k>=0}(-1)^k/(2k+1)^3 = Pi^3/32, arXiv:1808.04717 [math.CO], 2018.

R. J. Mathar, Table of Dirichlet L-series and prime zeta modulo functions for small moduli, arXiv:1008.2547 [math.NT], 2010-2015, section 2.2 entry L(m=4,r=2,s=3).

FORMULA

chi4(k) = Kronecker(-4, k); chi4(k) is 0, 1, 0, -1 when k reduced modulo 4 is 0, 1, 2, 3, respectively; chi4 is A101455.

Series: L(3, chi4) = Sum_{k>=1} chi4(k) k^{-3} = 1 - 1/3^3 + 1/5^3 - 1/7^3 + 1/9^3 - 1/11^3 + 1/13^3 - 1/15^3 + ...

Series: L(3, chi4) = Sum_{k>=0} tanh((2k+1) Pi/2)/(2k+1)^3. [Ramanujan; see Berndt, page 293]

Closed form: L(3, chi4) = Pi^3/32.

Equals Sum_{n>=0} (-1)^n/(2*n+1)^3. [Jean-Fran├žois Alcover, Mar 29 2013]

EXAMPLE

L(3, chi4) = Pi^3/32 = 0.9689461462593693804836348458469186...

MATHEMATICA

nmax = 1000; First[ RealDigits[Pi^3/32, 10, nmax] ]

PROG

(PARI) Pi^3/32 \\ Michel Marcus, Aug 15 2018

CROSSREFS

Cf. A153072, A153073, A153074, A175570, A175571, A175572.

Cf. A233091, A251809. [Bruno Berselli, Dec 10 2014]

Sequence in context: A138500 A161484 A103985 * A086279 A155533 A083281

Adjacent sequences:  A153068 A153069 A153070 * A153072 A153073 A153074

KEYWORD

nonn,cons,easy

AUTHOR

Stuart Clary, Dec 17 2008

EXTENSIONS

Offset corrected by R. J. Mathar, Feb 05 2009

STATUS

approved

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Last modified December 15 09:05 EST 2019. Contains 329995 sequences. (Running on oeis4.)