The even part of a positive integer is defined by
where is the exponent of the exact power of 2 dividing . The values for , 2, ..., are 1, 2, 1, 4, 1, 2, 1, 8, 1, 2, 1, ... (OEIS A006519). The even part function can be implemented in the Wolfram Language as
EvenPart[0]:=1 EvenPart[n_Integer]:=2^IntegerExponent[n,2]
More things to try:
Weisstein, Eric W. "Even Part." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/EvenPart.html