function magicSquare = oddmagic(dim)
% ODDMAGIC magic square of of odd numbered dimensions
%
% a = oddmagic(dim) produces a magic square of dimensions dim.
% oddmagic returns an error if dim is an even number. for even numbered
% magic squares use evenmagic. the smallest dimension accepted is 3.
%
% Algorithm developed by Sri. Samavedula Sita Rama Sastry
% http://www.me.berkeley.edu/~srinath/magic

if ( mod(dim, 2) == 0 )
	error('Error: oddmagic only works for odd numbers, try evenmagic for even sided magic squares');
end
if ( dim < 3 )
	error('Error: Smallest odd sided magic square possible is 3 x 3');
elseif ( dim == 3)
	magicSquare = magic(3);
	return;
end

magicSquare = zeros(dim, dim);

lastsmall = (dim^2 - (dim-2)^2)/2;
middleoddnum = lastsmall/2 - 1;

magicSquare(2:((middleoddnum-1)/2+1),1) = [1:2:(middleoddnum - 2)]';
magicSquare(dim, (dim+1)/2) = middleoddnum;

magicSquare((middleoddnum-1)/2+2:dim-1, dim) = [(middleoddnum + 2):2:lastsmall-1]';

magicSquare(dim, 2:((middleoddnum-1)/2+1)) = [2:2:(middleoddnum - 1)];
magicSquare(1, ((middleoddnum-1)/2+3):dim-1) = [(middleoddnum + 1):2:lastsmall-4];

magicSquare(1,1) = lastsmall - 2;
magicSquare(1,dim) = lastsmall;

outersum = 1+dim^2;
for i=2:dim-1
	emptyrow = dim;
	if (magicSquare(1,i) == 0) 
		emptyrow = 1;
	end
	magicSquare(emptyrow, i) = outersum - magicSquare(dim-emptyrow+1, i);
	emptycol = dim;
	if (magicSquare(i,1) == 0) 
		emptycol = 1;
	end
	magicSquare(i, emptycol) = outersum - magicSquare(i, dim-emptycol+1);
end
magicSquare(dim,1) = outersum - magicSquare(1,dim);
magicSquare(dim,dim) = outersum - magicSquare(1,1);

magicSquare(2:dim-1, 2:dim-1) = oddmagic(dim-2) + lastsmall;