Determine the value of 21+31+41+⋯+2017112016+22015+32014+⋯+20161.
Solution — click to reveal
We can write 12016+22015+32014+⋯+20161=12017−1+22017−2+32017−3+⋯+20162017−2016=12017−1+22017−1+32017−1+⋯+20162017−1=12017+22017+32017+⋯+20162017−2016=2017(21+31+⋯+20161)+1=2017(21+31+⋯+20161+20171).Therefore, 21+31+41+⋯+2017112016+22015+32014+⋯+20161=2017.