July 4th, 2016, 06:54 AM  #1 
Banned Camp Joined: Dec 2013 Posts: 1,117 Thanks: 41  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? 
July 4th, 2016, 08:38 AM  #2 
Banned Camp Joined: Dec 2013 Posts: 1,117 Thanks: 41 
Sorry for the mistake : a is an odd number >2 As I can not edit it sorry. 
July 8th, 2016, 08:14 AM  #3 
Banned Camp Joined: Dec 2013 Posts: 1,117 Thanks: 41 
Expanding k could lead to a factorization and consequently to a definitive proof. But how to do it? 

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