1+3+5+7+9+11+13+15+17+19…… +2005 = what's the second power

1+3+5+7+9+11+13+15+17+19…… +2005 = what's the second power

1+3+5+7+9+11+13+15+17+19…… +2005
=(1+2005)*((2005-1)/2 + 1)/2
=2006*2006/4
=1003²