Problems & Puzzles: Puzzles

Puzzle 800. A nice numbers sequence. Abhiram R. Devesh sent the following nice puzzle. I would like to propose a special prime that is formed by concatenating odd numbers on the right of "1" and even numbers on the left of "1".   Examples.   a) for n=3, the number generated is 213 (Not Prime)   b) for n=6, the number generated is 642135 (Not Prime) c) The first prime is generated for n=121 (255 digit long) 120118116114112110108106104102100989694929088868482807876747270\ 68666462605856545250484644424038363432302826242220181614121086\ 42135791113151719212325272931333537394143454749515355575961636\ 567697173757779818385878991939597991011031051071091111131151171\ 19121 Q. Can you find the next three primes?

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Contributions came from Jeff Heleen and Vicente Felipe Izquierdo

Jeff wrote

"...a prime is found when n=121 (255 digits)..." [already reported by Abhiram, see above]

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Vicente wrote:

For n<=4500 the other only solution I found is n=1399 with length 4489.

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