la numere consecutive , folosim formula
1 / n · ( n+1 ) = 1 / n - 1 /( n +1)
n= 1/1 - 1/2 + 1/2 -1/3 + 1/3 -1/4 +.... + 1 /2007 - 1/2008
simplificare , dar
n = 1/1 - 1 /2008 =1 - 1/2008 = ( 2008 -1 ) / 2008 = 2007 / 2008 = 0,99
[ n ] = [ 2007 / 2008 ] = 0