\\ mask of values seen on rows/columns/diagonals
row = vector(2000)
col = vector(#row)
dia = vector(2*#row-1)

{
	for (a=1, #row,
		ant = 0;	\\ mask of values seen on this antidiagonal
		for (c=1, a,
			r = a-c+1;
			d = #row - r + c;
			x = bitor(bitor(row[r],col[c]),bitor(dia[d],ant));
			v = valuation(1+x,2);
			m = 2^v;

			row[r] += m;
			col[c] += m;
			dia[d] += m;
			ant    += m;

		);
		print (a-1 " " v);
	);
}

quit