  Let $\sum_{d|n}$ denote sum over divisors of a positive integer $n$, and
$t_{r}(n)$ denote the number of representations of $n$ as a sum of $r$
triangular numbers. Then we prove that $$
\sum_{d|n}\frac{1+2\,(-1)^{d}}{d}=\sum_{r=1}^{n}\frac{(-1)^{r}}{r}\,
\binom{n}{r}\, t_{r}(n) $$ using a result of Ono, Robbins and Wahl.
