[seqfan] Re: A001576

[Richard Mathar]

vl> From seqfan-bounces at list.seqfan.eu Tue Feb 10 18:24:02 2009
vl> Date: Tue, 10 Feb 2009 17:40:26 +0100 (GMT+01:00)
vl> From: "vincenzo.librandi at tin.it" <vincenzo.librandi at tin.it>
vl> Subject: [seqfan]  A001576
vl> 
vl> Conjecture
vl>  If a(n) =1^n+2^n+4^n= prime number,
vl>    then
vl>    n is the 
vl> form
vl>    3^h.
vl> 
vl> Example:
vl>    For h=1, n=3, and 1^3+2^3+4^3=73 (prime)
vl>    
vl> h=2, n=9,
vl> and
vl>    1^9+2^9+4^9=262657 (prime)
vl>    Regards,
vl>    Vincenzo 
vl> Librandi

This is not new, see the Tony's comment in A051154.