Hypnosis
=60%+60%(0.3)
=78%
Each positive stage of Accuracy on user (equivalently, negative stage of Evasion on target) gives +1/3 of the base accuracy. In other words, the stages of Accuracy have the following modifiers to base accuracy:
+0 => 1
+1 => 4/3
+2 => 5/3
+3 => 2
+4 => 7/3
+5 => 8/3
+6 => 3
The modifier for the negative stages of Accuracy on user (or positive stages of Evasion on target) are just the reciprocals of the above modifiers since +X stages should be canceled out by -X stages:
-6 => 3/9
-5 => 3/8
-4 => 3/7
-3 => 3/6
-2 => 3/5
-1 => 3/4
-0 => 1
Consider a move with 60% base accuracy (e.g., Hypnosis). Each positive stage of Accuracy on the user gives an additional 20% base accuracy to the move (since 20% is 1/3 of 60%). So the accuracy of Hypnosis is given by the following:
-6 => 20%
-5 => 22% (round down from 22.5%)
-4 => 25% (round down from 25.714%)
-3 => 30%
-2 => 36%
-1 => 45%
0 => 60%
+1 => 80%
+2 => 100%
As someone wrote earlier...
Any move with 75% or more base accuracy becomes 100% after +1 Accuracy.
Any move with 60% or more base accuracy becomes 100% after +2 Accuracy.
Any move with 50% or more base accuracy becomes 100% after +3 Accuracy.
There are no moves that have less than 50% accuracy which are also affected by accuracy checks. (OHKO moves likes Sheer Cold have a different accuracy formula that is not affected by changes in Accuracy or Evasion. Their accuracy is always 30% plus an additional 1% for each level the user is above the target. But they are not allowed in any Smogon tier anyway, so the entire issue is moot.)