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The site-perimeter of compositions

  • Aubrey Blecher EMAIL logo , Charlotte Brennan and Arnold Knopfmacher
Published/Copyright: April 13, 2022

Abstract

Compositions of n are finite sequences of positive integers (σi)i=1k such that

σ1+σ2++σk=n.

We represent a composition of n as a bargraph with area n such that the height of the i-th column of the bargraph equals the size of the i-th part of the composition. We consider the site-perimeter which is the number of nearest-neighbour cells outside the boundary of the polyomino. The generating function that counts the total site-perimeter of compositions is obtained. In addition, we rederive the average site-perimeter of a composition by direct counting. Finally we determine the average site-perimeter of a bargraph with a given semi-perimeter.


Note: Originally published in Diskretnaya Matematika (2022) 34,№1, 3–19 (in Russian).


  1. Funding: The work of Charlotte Brennan was supported by the National Research Foundation under grant number 86329. The work of Arnold Knopfmacher was supported by the National Research Foundation under grant number 81021.

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Received: 2021-09-01
Published Online: 2022-04-13
Published in Print: 2022-04-26

© 2022 Walter de Gruyter GmbH, Berlin/Boston

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