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{{Short description|Type of sequence of numbers}}
[[File:Pascal's_triangle_5.svg|thumb|The rows of Pascal's triangle are examples for logarithmically concave sequences.]]
In [[mathematics]], a sequence {{math|''a''}} = {{math| (''a''<sub>0</sub>, ''a''<sub>1</sub>, ..., ''a''<sub>''n''</sub>)}} of nonnegative real numbers is called a '''logarithmically concave sequence''', or a '''log-concave sequence''' for short, if {{math|''a''<sub>''i''</sub><sup>2</sup> ≥ ''a''<sub>''i''−1</sub>''a''<sub>''i''+1</sub>}} holds for {{math|0 < ''i'' < ''n'' }}.
 
'''Remark:''' some authors (explicitly or not) add two further conditions in the definition of log-concave sequences:
* {{math|''a''}} is non-negative
* {{math|''a''}} has no internal zeros; in other words, the [[Support (mathematics)|support]] of {{math|''a''}} is an interval of {{math|'''Z'''}}.
These conditions mirror the ones required for [[Logarithmically_concave_function|log-concave functions]].
 
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{{Reflist}}
 
* {{cite journal|last=Stanley|first=R. P.|authorlink=Richard P. Stanley|title=Log-Concave and Unimodal Sequences in Algebra, Combinatorics, and Geometry|journal=[[Annals of the New York Academy of Sciences]]|date=December 1989|volume=576|issue=1 |pages=500–535|doi= 10.1111/j.1749-6632.1989.tb16434.x|bibcode=1989NYASA.576..500S }}
 
==See also==