自然数方幂的累进和

设S_t(n)=1~t+2~t+…+n^t,SS_t(n)=sum from i=1 to n sum from j=1 to i (j^t)=1~t+(1~t+2~t)+…+(1~t+2~t+…+n^t),t∈N,并称SS_t(n)为自然数方幂的累进和。文[1]给出: