I think, the statement of the problem is not complete. The reference problem is not available. I know very well about right angle triangles but I do not have the idea on how to find the solutions. Please help me out.

c=[];
for A=1:p
B=0;
while B < 1000
B = B+1;
C = sqrt((A^2) + (B^2));
perimeter = A+B+C;
if perimeter==p
c(end+1,:) = [A,B,C];
end
end
end
c=unique(sort(c,2),'rows');
x=cell(1,size(c,1));
for i=1:size(c,1)
[x{1,i}]= deal(c(i,:))
end
c=x

Works, but is horribly inefficient especially for higher p...

solution using a Neural Network Toolbox function ;)