Trivia

Subject:
Puzzler -- PINs

Alex Y
A bank assigns 4-digit PINs to their customers' ATM cards. They use all the digits (including leading zeros). But fearing that some customers may be superstitious, they make it a practice never to have "13" appear in the PIN. I.e., "4153" is a legitimate PIN, but "4135" is not.

How many unique PINs can they assign using with this restriction in place?

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