Hans-Egon Richert

Hans-Egon Richert (June 2, 1924 – November 25, 1993) was a German mathematician who worked primarily in analytic number theory.

For many years he was a chairman of the Analytic Number Theory meetings at the Mathematical Research Institute of Oberwolfach.

[2] Richert made contributions to additive number theory, Dirichlet series, Riesz summability, the multiplicative analog of the Erdős–Fuchs theorem, estimates of the number of non-isomorphic abelian groups, and bounds for exponential sums.

He proved the exponent 15/46 for the Dirichlet divisor problem, a record that stood for many years.

[3]: 257 Richert also produced a "readable form"[2] of Chen's theorem (it is covered in the last chapter of Sieve Methods[1]).