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 A129660 Numerators of the Engel partial sums for L(3, chi3), where L(s, chi3) is the Dirichlet L-function for the non-principal character modulo 3. 15
 0, 1, 3, 7, 99, 9307, 3462205, 401327263, 5290639975663, 21886143096656843, 32306573547837099089161, 2837034062676862693613762377, 182184397885888753164448171682621 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES Leonhard Euler, "Introductio in Analysin Infinitorum", First Part, Articles 176 and 292 LINKS FORMULA chi3(k) = Kronecker(-3, k); chi3(k) is 0, 1, -1 when k reduced modulo 3 is 0, 1, 2, respectively; chi3 is A049347 shifted. Series: L(3, chi3) = Sum_{k>=1} chi3(k) k^{-3} = 1 - 1/2^3 + 1/4^3 - 1/5^3 + 1/7^3 - 1/8^3 + 1/10^3 - 1/11^3 + ... Closed form: L(3, chi3) = 4 Pi^3/(81 sqrt(3)). EXAMPLE L(3, chi3) = 0.8840238117500798567430579168710118077... = 1/2 + 1/(2*2) + 1/(2*2*2) + 1/(2*2*2*14) + 1/(2*2*2*14*94) + ..., the partial sums of which are 0, 1/2, 3/4, 7/8, 99/112, 9307/10528, ... MATHEMATICA nmax = 100; prec = 2000 (* Adjust the precision depending on nmax. *); c = N[ 4 Pi^3/(81 Sqrt[3]), prec]; e = First@Transpose@NestList[{Ceiling[1/(#[[1]] #[[2]] - 1)], #[[1]] #[[2]] - 1}&, {Ceiling[1/c], c}, nmax - 1]; Numerator[ FoldList[Plus, 0, 1/Drop[ FoldList[Times, 1, e], 1 ] ] ] CROSSREFS Cf. A129404, A129405, A129406, A129407, A129408, A129409, A129410, A129411. Cf. A129658, A129659, A129661, A129662, A129663, A129664, A129665. Sequence in context: A074349 A159310 A299377 * A243734 A158467 A260824 Adjacent sequences:  A129657 A129658 A129659 * A129661 A129662 A129663 KEYWORD nonn,frac,easy AUTHOR Stuart Clary, Apr 30 2007 STATUS approved

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Last modified February 24 17:29 EST 2020. Contains 332209 sequences. (Running on oeis4.)