On the variance of the digits of $1/p$
Number Theory
2026-05-21 v3
Abstract
Let be a prime and an integer such that does not divide . Then has a periodic digit expansion with respect to the basis . The length of the period is the (multiplicative) order of mod . In the case a formula for the variance of the digits of a period was given previously. This formula involves a Dedekind sum. We determine the variance in the case . If mod 4 a Dedekind sum and the class number of occur in the respective formula. If mod 4, the formula may be much more complex since it involves linear combinations of (possibly many) products of two Bernoulli numbers attached to odd characters.
Keywords
Cite
@article{arxiv.2601.08416,
title = {On the variance of the digits of $1/p$},
author = {Kurt Girstmair},
journal= {arXiv preprint arXiv:2601.08416},
year = {2026}
}