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A sequence $(a_n)$ is said to be log-concave provided $a_i^2 \geq a_{i-1}a_{i+1}$ for all $i$.

What sorts of intuition can one have about log-concave sequences? In particular, what kind of "picture" does the property of log-concavity conjure up with regard to its graph?

What nice things happen when a sequence is log-concave? What are typical "next steps" after one has established the log-concavity of a sequence?

Any other comments related to getting a feel for log-concave sequences are most welcome.

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Have you looked, for example, at ? – Qiaochu Yuan Sep 19 '10 at 21:20
Sorry for the unintended bump. I meant only to test the rollback feature. – Austin Mohr Sep 28 '10 at 0:42

As for nice properties of log-concave functions, there are many applications in probability. For example, if the PDF of a function is log-concave, so is the CDF.

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