(log23+log49+....+以2的n次方为底3的n次方的对数）乘以log98的n次方根[利用对数的换底公式]=[ln3/ln2+2ln3/(2ln2)+...+nln3/(nln2)][nln8/(2ln3)]=[ln3/ln2][1+1+...+1][3nln2/(2ln3)]=n[3n/2]=3n^2/2
