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No primes 3 (Posted on 2019-08-10) Difficulty: 2 of 5
Start with the numbers x1=9 and x2=20. After that, each number xn=2xn-1+xn-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    
Rating: 5.0000 (1 votes)

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re: Possible solutionMath Man2019-08-13 07:01:54
Some ThoughtsPossible solutionbroll2019-08-10 23:12:09
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