试题 试卷
题型:单选题 题类:常考题 难易度:容易
l+2+3+…+n= n(n+l);
l+3+6+…+ n(n+1)= n(n+1)(n+2);
1+4+10+… n(n+1)(n+2)= n(n+1)(n+2)(n+3);
可以推测,1+5+15+…+ n(n+1)(n+2)(n+3)={#blank#}1{#/blank#}.
试题篮