Summation Notation
First Constant Rule
![\[ \mbox{\Large\displaystyle\sum\limits_{i=x}^n a = \normalsize\displaystyle(n-x+1)a } \]](http://entitycs.net/wordpress/wp-content/ql-cache/quicklatex.com-aecfca4ae687bb6f4919032059a54227_l3.png "Rendered by QuickLaTeX.com")
where 
is an expression
![\[ \mbox{\Large\displaystyle\sum\limits_{i=x}^n x_{ij}} \]](http://entitycs.net/wordpress/wp-content/ql-cache/quicklatex.com-65ed0df3a9063825414dcdbaf38a96fb_l3.png "Rendered by QuickLaTeX.com")
where 
and 
are indexes in a 2-dimensional list
// variables int n, i = 0; Expression a;
Variables: 
Single Subscript Notation
.
where is an expression
where and are indexes in a 2-dimensional list
// variables int n, i = 0; Expression a;
Variables:
Single Subscript Notation
.