See that odd number are in a Aritmetic progression with a1 = 1 and r = 2
30th number of sequence is given by:
[tex]a_{30}=a_1+29r\\
\\
a_{30}=1+29*2\\
\\
a_{30}=59[/tex]
Now you can calculate the sun by:
[tex]S_{30}=\frac{30(1+59)}{2}=\frac{30*60}{2}=900[/tex]
