mathlib3

de76acdc - feat(number_theory/arithmetic_function): moebius is the inverse of zeta (#5001)

feat(number_theory/arithmetic_function): moebius is the inverse of zeta (#5001) Proves the most basic version of moebius inversion: that the moebius function is the inverse of the zeta function Co-authored-by: jalex-stark <alexmaplegm@gmail.com>