Some generalizations of Olivier's theorem
Let $\sum\limits_{n=1}^\infty a_n$ be a convergent series of positive real numbers. L. Olivier proved that if the sequence $(a_n)$ is non-increasing, then $\lim\limits_{n \to\infty} n a_n = 0$. In the present paper: (a) We formulate and prove a necessary and sufficient condition for having $\lim\lim...
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Published in | Mathematica bohemica Vol. 141; no. 4; pp. 483 - 494 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Institute of Mathematics, Czech Academy of Sciences
01.01.2016
Institute of Mathematics of the Czech Academy of Science |
Subjects | |
Online Access | Get full text |
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Summary: | Let $\sum\limits_{n=1}^\infty a_n$ be a convergent series of positive real numbers. L. Olivier proved that if the sequence $(a_n)$ is non-increasing, then $\lim\limits_{n \to\infty} n a_n = 0$. In the present paper: (a) We formulate and prove a necessary and sufficient condition for having $\lim\limits_{n \to\infty} n a_n = 0$; Olivier's theorem is a consequence of our Theorem \ref{import}. (b) We prove properties analogous to Olivier's property when the usual convergence is replaced by the $\mathcal I$-convergence, that is a convergence according to an ideal $\mathcal I$ of subsets of $\mathbb N$. Again, Olivier's theorem is a consequence of our Theorem \ref{Iol}, when one takes as $\mathcal I$ the ideal of all finite subsets of $\mathbb N$. |
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ISSN: | 0862-7959 2464-7136 |
DOI: | 10.21136/MB.2016.0057-15 |