Killbots Number

Killbot's Number is an unimaginably large number, that was made personally by Killbot. It also can be defined as size of the Multiverse.
== How to calculate ==
let's imagine number i0
i0 is pretty small, i0 = 2^2
not so large
i1, then
i0 = 4
i1 = i0^i0^i0^i0 = 4^4^4^4 (4^ repeated 4 times) = 340282366920938463463374607431768211456
not so small, isn't it?
i2, then
i2 = i1^i1^i1^i1^i1....... (i1 times in total)
it's extremely large
even i2 is incalculable
then...
i3 = i2^i2^i2........ (i2 times)
repeating...
i42 = Killbots number
This function has a growth rate of approximately 4 in the FGH, making i42 smaller than Graham's Number (who's function has a growth rate of omega+1).