Christian Krattenthaler, Thomas W. Müller. Free subgroup numbers modulo prime powers: The non-periodic case. Journal of Combinatorial Theory, Series A, 154:49-76, 2018. [doi]
@article{KrattenthalerM18,
title = {Free subgroup numbers modulo prime powers: The non-periodic case},
author = {Christian Krattenthaler and Thomas W. Müller},
year = {2018},
doi = {10.1016/j.jcta.2017.08.007},
url = {https://doi.org/10.1016/j.jcta.2017.08.007},
researchr = {https://researchr.org/publication/KrattenthalerM18},
cites = {0},
citedby = {0},
journal = {Journal of Combinatorial Theory, Series A},
volume = {154},
pages = {49-76},
}