Medium
In the sequence 4727235974752479478471, how many '7's are there which are immediately preceded by '4' but NOT immediately followed by '2'?
Explanation
Explanation
Scanning the sequence 4-7-2-7-2-3-5-9-7-4-7-5-2-4-7-9-4-7-8-4-7-1 position by position, the 7's that come right after a '4' AND are NOT followed by a '2' occur four times: after the 4 before '5', after the 4 before '9', after the 4 before '8', and after the final 4 before '1'. So the count is 4.
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