[seqfan] A175287: n = 3^k3 + 5^k5 + 7^k7

[zak seidov]

Open to discussion (not submitted yet),
thanks,
Zak

%I A175287
%S A175287 135,255,375,2535,3135,3155,3255
%N A175287 Numbers n with two representations as the sum of positive powers of 3,5 and 7. 
%C A175287 Except of 3155 all terms are divisible by 15.
%C A175287 No other terms <7^180 (<132*10^150).
%C A175287 Values of {k3,k5,k7}:
%C A175287 n=135, {1,3,1},{4,1,2}
%C A175287 n=255, {4,3,2},{5,1,1}
%C A175287 n=375, {3,1,3},{5,3,1}
%C A175287 n=2535, {2,3,4},{7,1,3}
%C A175287 n=3135, {1,5,1},{6,1,4}
%C A175287 n=3155, {6,2,4},{7,4,3}
%C A175287 n=3255, {4,5,2},{6,3,4}. 
%F A175287  
%Y A175287 135=3+25+7=81+5+49, 255=81+125+49=243+5+7, 375=27+5+343=243+125+7. 
%K A175287 nonn
%O A175287 1,1
%A A175287 Zak Seidov (zakseidov(AT)yahoo.com), Mar 22 2010