n +(n+1) +(n+2)+.......+(n+1996) = 1997^1998
1997·n + (1+2+3+........+1996) = 1997^1998
1997n+ 1996·1997/2 = 1997^1998
n +998= 1997^1997
n = 1997^2-998
S=(1997^2-998)+(1997^2-997)+(1997^2-996)+...+(1999^2000+998)
verificare nr termeni 998-(-998)+1=1997
