P$($n$)$: $02+12+22+...+$ n$2=$ n$($n $+1)(2$n $+1)/6,$ n$>=0.$

If n $=0,$ then the left$-$hand side of P$(0)=02=0,$ and right$-$hand side of P$(0)=0\backslash$times $(0+1)(2\backslash$times $0+1)/6=0.$

What is the right$-$hand side of P$($n$+1)?$