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No primes 3 (Posted on 2019-08-10)

Start with the numbers x₁=9 and x₂=20. After that, each number x_n=2x_n-1+x_n-2.

x₃=2x₂+x₁=2(20)+9=40+9=49
x₄=2x₃+x₂=2(49)+20=98+20=118
x₅=2x₄+x₃=2(118)+49=236+49=285
...

This gives the sequence 9, 20, 49, 118, 285, ... Prove that no number in this sequence is prime.

No Solution Yet Submitted by Math Man

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