Assume this is meant to be: 52+62+72+82+92+102+202, then between 52 and 102 we have an arithmetic progression in which the first term is 52 and the common difference is 10; however there is a gap after 102, and 112 is not the next term, because 202 takes its place. But the series terminates at 202. We could simply add the terms to get 664; or we could sum the AP for terms 52 to 102. 102+52=154=62+92=72+82. So that's 3*154=462, then add in the last term, 202=664.