Recursive definition of sum of first nnn numbers S(n)S(n)S(n)?
S(n)=S(n+1)−nS(n) = S(n+1) - nS(n)=S(n+1)−n
S(n)=n+S(n−1)S(n) = n + S(n-1)S(n)=n+S(n−1)
S(n)=n2S(n) = n^2S(n)=n2
S(n)=n(n+1)/2S(n) = n(n+1)/2S(n)=n(n+1)/2