Journal of Integer Sequences, Vol. 29 (2026), Article 26.1.5

Integer Sequences for Diversity Statistics


Bradley K. Moon and Noah A. Rosenberg
Department of Biology
Stanford University
Stanford, CA 94305
USA

Abstract:

Consider a discrete set of objects and a sample of size N taken with replacement from the set, producing a list of counts of the objects that corresponds to a partition of N . Two statistics that are commonly used for measuring the "diversity" of the sample are the Gini-Simpson index and the Shannon index. We study the number of possible values that these indices can take across all possible partitions of the sample size N as N increases. The two statistics are highly correlated over the set of partitions of N. However, the number of possible values that the Shannon index can take (A383683) far exceeds the number of possible values of the Gini-Simpson index (A069999), with the latter growing quadratically and the former growing faster than every polynomial.


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(Concerned with sequences A000041 A000607 A006463 A069999 A381811 A383682 A383683.)


Received May 20 2025; revised versions received May 21 2025; December 19 2025; February 10 2026. Published in Journal of Integer Sequences, February 10 2026.


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