The sum of powers of even divisors of a number. It is the analog of the divisor function for even divisors only and is written . It is given simply in terms of the usual divisor function by
(1)

The sum of powers of even divisors of a number. It is the analog of the divisor function for even divisors only and is written . It is given simply in terms of the usual divisor function by
(1)

Weisstein, Eric W. "Even Divisor Function." From MathWorldA Wolfram Web Resource. https://mathworld.wolfram.com/EvenDivisorFunction.html