So:12+22+32+42+...+(n+1) 2 = (n+1) (n+1+1) (2
So: Tn=b 1+b2+b3+...+bn.
=-2^2/4-3^2/4-4^2/4-...-(n+ 1)^2/4
=-(2^2+3^2+4^2+...+(n+ 1)^2)/4
=-( 1^2+2^2+3^2+4^2+...+(n+ 1)^2- 1^2)/4
=-( 1^2+2^2+3^2+4^2+...+(n+ 1)^2)/4+ 1^2/4
=-(n+ 1)(n+2)(2n+3)/24+ 1/4
Reference:/link? URL = 7 Yb RSC 4 cz 27 nqyvkrsynfosnakdulq 3 bzbf 08 i3 ppu 1 wov 6 qqdx-0 fy r6k 1 seyakrjqxbzp 88 _ hnjutx 1 p9bk