Takemiya Double Kosumi
This is a special pattern played often by Takemiya, when the sanrensei is developed with both marked stones.
White invades at 1 and Black uses 2 and 4 to build influence. After White 11 at a Black doesn't connect on the right, but presses once again at b, to continue with a consistent central policy.
An example for that opening can be found at A 4-4 and 3-5 strategy, example 1