For GARTH(n), hexate n to n copies of n concatenated, call it it GARTH1(n) and then hexate that number to n copies of n concatenated, GARTH1(n) times. Example: GARTH(3) = (....(((3^^^^333)^^^^333)^^^^333)...^^^333 with 3^^^^333 hexations.
Example 2: GARTH(5) = (....(((5^^^^55,555)^^^^55,555)^^^^55,555)...^^^55,555 with 5^^^^55,555 hexations.
GARTHX(n) is to hexate n to GARTH(n), n^^^^GARTH(n) times.
Example: GARTHX(3) = (....(((3^^^^GARTH(3))^^^^GARTH(3))^^^^GARTH(3))...^^^GARTH(3) with 3^^^^GARTH(3) hexations.
GARTHY(n) is to hexate n to GARTHX(n), n^^^^GARTHX(n) times.
Example: GARTHY(3) = (....(((3^^^^GARTHX(3))^^^^GARTHX(3))^^^^GARTHX(3))...^^^GARTHX(3) with 3^^^^GARTHX(3) hexations.
GARTHZ(n) is to hexate n to GARTHY(n), n^^^^GARTHY(n) times.
Example: GARTHZ(3) = (....(((3^^^^GARTHY(3))^^^^GARTHY(3))^^^^GARTHY(3))...^^^GARTHY(3) with 3^^^^GARTHY(3) hexations.