J jacks Dec 2010 107 3 Jan 28, 2019 #1 Finding value of \(\displaystyle \displaystyle \mathop{\sum\sum\sum\sum}_{1\leq i\leq j<k\leq w\leq n}1\)

Finding value of \(\displaystyle \displaystyle \mathop{\sum\sum\sum\sum}_{1\leq i\leq j<k\leq w\leq n}1\)