26 November 2015

Logical sequence (Quiz of 25 Nov 2015)

This question proved difficult and very few teams got the answer last night.
Cette question s'est avérée difficile et peu d'équipes ont trouvé la bonne réponse hier soir.

What number comes next in the sequence:
13, 17, 31, 37, 71, 73, 79, 97 …?

Quelle est la suite de cette séquence :
13, 17, 31, 37, 71, 73, 79, 97 … ?

(Hint: I didn't ask where the sequence could have started.)
(Indice: Je ne demande pas où la séquence aurait pu commencer.)


Skibbereen Eagle said...

Sequence of emirps - 107

emirp (prime spelled backwards) is a prime number that results in a different prime when its decimal digits are reversed. Can't see it helping to work out the price of a litre of beer any day soon!

Páraic Maguire said...

Not bad! But not the answer I was looking for. I didn't say the number, when reversed, had to be a different prime number. So, 101 is the answer.

As others have commented, I didn't start at 11, but there is no reason why I should. If the question concerned the next in the sequence "-4, -2, 0, 2, 4 ..." you could say "Why didn't you start at -6?" And so on.

And remember the Golden Rule: the correct answer to every question is the answer defined by Mr Quiz ;-)