Mihai Ciucu, Christian Krattenthaler. The Number of Centered Lozenge Tilings of a Symmetric Hexagon. Journal of Combinatorial Theory, Series A, 86(1):103-126, 1999. [doi]
@article{CiucuK99,
title = {The Number of Centered Lozenge Tilings of a Symmetric Hexagon},
author = {Mihai Ciucu and Christian Krattenthaler},
year = {1999},
doi = {10.1006/jcta.1998.2918},
url = {http://dx.doi.org/10.1006/jcta.1998.2918},
researchr = {https://researchr.org/publication/CiucuK99},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {86},
number = {1},
pages = {103-126},
}