The number of polyiamonds is supermultiplicative
The electronic journal of combinatorics, Tome 30 (2023) no. 4
While the number of polyominoes is known to be supermultiplicative by a simple concatenation argument, it is still unknown whether the same applies to polyiamonds. This article proves that if $\ell,m$ are not both $1$, then $T(\ell+m)\ge T(\ell)T(m)$, for which one can say that the number of polyiamonds $T(n)$ is supermultiplicative. The method is, however, by concatenating, merging and adding cells at the same time. A corollary is an increment of the best known lower bound on the growth constant from $2.8423$ to $2.8578$.
DOI :
10.37236/12028
Classification :
05B50, 05A16, 05A15
Mots-clés : polyominoes, equivalent lattice animals
Mots-clés : polyominoes, equivalent lattice animals
Affiliations des auteurs :
Vuong Bui  1
@article{10_37236_12028,
author = {Vuong Bui},
title = {The number of polyiamonds is supermultiplicative},
journal = {The electronic journal of combinatorics},
year = {2023},
volume = {30},
number = {4},
doi = {10.37236/12028},
zbl = {1532.05035},
url = {http://geodesic.mathdoc.fr/articles/10.37236/12028/}
}
Vuong Bui. The number of polyiamonds is supermultiplicative. The electronic journal of combinatorics, Tome 30 (2023) no. 4. doi: 10.37236/12028
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