On an optimality property of Ramanujan sums
On an optimality property of Ramanujan sums
We evaluate <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="inf Underscript b Subscript n Endscripts sigma-summation Underscript a equals 1 Overscript q Endscripts StartAbsoluteValue sigma-summation Underscript StartLayout 1st Row n equals 1 left-parenthesis n comma q right-parenthesis equals 1 EndLayout Overscript q Endscripts b Subscript n Baseline e Superscript 2 pi i a …