Ulrich Tamm. Size of downsets in the pushing order and a problem of Berlekamp. Discrete Applied Mathematics, 156(9):1560-1566, 2008. [doi]
@article{Tamm08-0,
title = {Size of downsets in the pushing order and a problem of Berlekamp},
author = {Ulrich Tamm},
year = {2008},
doi = {10.1016/j.dam.2006.11.022},
url = {http://dx.doi.org/10.1016/j.dam.2006.11.022},
researchr = {https://researchr.org/publication/Tamm08-0},
cites = {0},
citedby = {0},
journal = {Discrete Applied Mathematics},
volume = {156},
number = {9},
pages = {1560-1566},
}