How many such 6's are there in the following number series, each of which is immediately preceded by 1 or 5 and immediately followed by 3 or 9?2 6 3 7 5 6 4 2 9 6 1 3 4 1 6 3 9 1 5 6 9 2 3 1 6 5 4 3 2 1 9 6 7 1 6 3
