On the law of the iterated logarithm for continued fractions with sequentially restricted partial quotients

We establish a law of the iterated logarithm (LIL) for the set of real numbers whose $n$-th partial quotient is bigger than ${\alpha }_n$, where $({\alpha }_n)$ is a sequence such that $\sum 1\mathrm{/}{\alpha }_n$ is finite. This set is shown to have Hausdorff dimension $1\mathrm{/}2$ in many cases and the measure in LIL is absolutely continuous to the Hausdorff measure. The result is obtained as an application of a strong invariance principle for unbounded observables on the limit set of a sequential iterated function system.