Which {\bf one} of the following series converges? (Note that, for a
real number~$x$, the notation $\allfloor x$ denotes
the greatest integer with is less than or equal to~$x$.)
\correct $\sum(-1)^n \frac{1}{\allfloor {n\pi}}$
\wrong $\sum\frac{1}{\sqrt n\log n}$
\wrong $\sum (-1)^n\sin(\frac{n\pi}6)$
\wrong $\sum (-1)^n\frac{n!}{2^n}$
\wrong $\sum \allfloor {{2^n}/{n^2}}$
