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%I #7 Jul 25 2013 04:36:53
%S 0,0,2,0,4,2,7,3,10,4,8,9,15,7,19,14,11,9,9
%N a(n) = number of integral positive unordered pairs (x,y) such that x^2+n*y=z^2 and n*x+y^2=w^2.
%C Solutions (x,y) and (y,x) count only once.
%e Example:
%e a(6)=2 since the system of two equations
%e 1. x^2+6y=z^2
%e 2. 6x+y^2=w^2
%e has the following 2 solutions:
%e s1. (x,y)=(2,2) yielding 2^2+6*2=16=4^2 and 6*2+2^2=16=4^2.
%e s2. (x,y)=(22,32) yielding 22^2+6*32=26^2 and 6*22+32^2=34^2.
%e There are no solutions for n= 1, 2, 4.
%K nonn
%O 1,3
%A _Carmine Suriano_, Jul 21 2009
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