> Let me attempt a patch, and please forgive my reopening the bug.
Here is that patch. Sadly mail to Florian Beck's address bounced but perhaps someone else will see the proposal and subject it to scrutiny. In short:
1. A sign mistake in the original code caused the infinite recursion. Fixed.
2. Some parts of the computation used tail recursion, which limited their applicability in elisp. Changed to use an imperative loop (alas).
3. The binomial coefficients have now been extended for all integral arguments, using definitions from ; see also  and .
 M. J. Kronenburg; The Binomial Coefficient for Negative Arguments; https://arxiv.org/abs/1105.3689  D. Loeb, E. Damiani and O. D’Antona; Getting Results with Negative Thinking; https://arxiv.org/abs/math/9502214  David Fowler; The Binomial Coefficient Function; The American Mathematical Monthly, Vol. 103, No. 1 (Jan., 1996), pp. 1-17