fact: Definition arithmetic_mean (R : numDomainType) (u_ : R ^nat) : R ^nat := [sequence n.+1%:R^-1 * (series u_ n.+1)]_n.
imports: mathcomp(all_ssreflect ssralg ssrint ssrnum matrix) mathcomp(interval rat) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(set_interval) reals ereal signed topology normedtype landau