Riley Vashtee: Find the next number in the sequence: 313, 331, 367…? What?
Martha Jones: You said the crew knew all the answers.
Riley Vashtee: The crew’s change since we’ve set the questions.
Martha Jones: You’re joking.
The Doctor: 379!
Martha Jones: What?
The Doctor: It’s a sequence of happy primes; 379.
Martha Jones: Happy what?
The Doctor: Just enter it!
Riley Vashtee: Are you sure? We only get one chance.
The Doctor: Any number that reduces to 1 when you take the sum of the square of its digits and you continue iterating until it yields 1 is a happy number. Any number that doesn’t, isn’t. A happy prime is a number which is both happy and prime, now type it in! I dunno, talk about dumbing down. Don’t they teach recreational mathematics anymore?

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