OFFSET
0,3
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).
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.
EXAMPLE
L(3, chi4) = 0.9689461462593693804836348458469186... = [0; 1, 31, 4, 1, 18, 21, 1, 1, 2, 1, 2, 1, 3, 6, 3, 28, ...].
MATHEMATICA
nmax = 1000; ContinuedFraction[Pi^3/32, nmax + 1]
CROSSREFS
KEYWORD
nonn,cofr,easy
AUTHOR
Stuart Clary, Dec 17 2008
STATUS
approved