2010-10-12から1日間の記事一覧
http://projecteuler.net/index.php?section=problems&id=12 The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be: 1, 3, 6…