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July 4th, 2016, 06:54 AM   #1
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Composite for ever

a is a positive integer>2
k is an odd integer
Let k=a^(a+1)+(a+1)^a

Examples :

a=3
k=3^4+4^3=145 is composite

If a>2 k is always composite.

True or false?
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July 4th, 2016, 08:38 AM   #2
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Sorry for the mistake : a is an odd number >2
As I can not edit it sorry.
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July 8th, 2016, 08:14 AM   #3
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Expanding k could lead to a factorization and consequently to a definitive proof.
But how to do it?
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