Upgrading from:

NumberTheory`Ramanujan`

RamanujanTau, RamanujanTauTheta, and RamanujanTauZ have been added to the built-in Mathematica kernel.
RamanujanTauDirichletSeries is now available as the newly added built-in Mathematica kernel function RamanujanTauL.

RamanujanTau

The first 10 nonzero values of RamanujanTau:

Version 5.2 << NumberTheory`Ramanujan`;
Table[RamanujanTau[n], {n, 1, 10}]

RamanujanTauDirichletSeries

The value of the Ramanujan Dirichlet L-function near the first zero of the critical line:

Version 5.2 << NumberTheory`Ramanujan`;
RamanujanTauDirichletSeries[6 + 9.22 I]

RamanujanTauGeneratingFunction was available in previous versions of Mathematica and is now available on the web at library.wolfram.com/infocenter/MathSource/6775.