Contact us
Choose a category below so we can get back to you as quickly as possible.
由1+3+6+10+15+21+28+36(高斯求和)=1+(1+2)+(1+2+3)+(1+2+3+4)+…+(1+2+…+5)+(1+2+…+6)+(1+2+…+7)+(1+2+…+8)=1×8+2×7+3×6+4×5…
We and our partners use cookies and other technologies to analyze traffic and optimize your experience. View more info and control your cookies settings at any time in our Cookies Policy.