Then sn = a1+a2+a3+...+an =1-1/2+1/3+1/4. ..
Another example.
Bn= 1/n- 1/(n+2), then BN-1=1(n-1)-1(n+/kloc-0 . . sn = 1- 1/3+ 1/2- 1/4+ 1/3- 1/5+......+ 1/(n-2)- 1/n+ 1/(n- 1)- 1/(n+ / kloc-0/)+ 1/n- 1/(n+2)= 1+ 1/2- 1/(n+ 1)- 1
Cumulative multiplication is similar.
bn=n/(n+ 1),bn- 1=(n- 1)/n,
cn=b 1*b2*b3*b4*.....* bn- 1 * bn = 1/2 * 2/3 * 3/4 *......(n- 1)/n * n/(n+ 1)= 1/(n+ 1) ...
bn=n/(n+2),bn- 1 =(n- 1)/(n+ 1),bn-2=(n-2)/n,
cn=b 1*b2*b3*....bn-2 * bn- 1 * bn = 1/3 * 2/4 * 3/5 * 4/6 *......*(n-2)/n *(n- 1)/(n+ 1)* n/(n+2)
= 1*2/((n+ 1)*(n+2))