1178 假设 n*(n+1)*(n+2)/6 = m * 10^n 科学计数法,这里m是一个小于10的正实数 则 log(n*(n+1)*(n+2)/6 ) == log(m) + n 令 log(n*(n+1)*(n+2)/6 ) - [(n*(n+1)*(n+2)/6 )] = a 则 m ==10^a n ==[(n*(n+1)*(n+2)/6 )] (取整)