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\vskip 1cm{\LARGE\bf On the Summation of Certain Iterated Series}
\vskip 1cm {\large
Ovidiu Furdui\\
Campia Turzii \\
405100 Cluj \\
Romania\\ 
\href{mailto:ofurdui@yahoo.com}{\tt ofurdui@yahoo.com}  \\
\ \\
Tiberiu Trif\\
Department of Mathematics\\
Babe\c{s}-Bolyai University \\
Cluj-Napoca \\
Romania\\
\href{mailto:ttrif@math.ubbcluj.ro}{\tt ttrif@math.ubbcluj.ro} \\
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\begin{abstract}
The paper gives a unified treatment of the summation of certain iterated series of the form
 $\sum_{n=1}^{\infty}\sum_{m=1}^{\infty}a_{n+m},$
where $(a_{n})_{n\in \mathbb{N}}$ is a sequence of real numbers. We prove that, under certain conditions, the double iterated series equals the difference of two single series.
\end{abstract}

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