n=1  —> 3    

n=2  —> 9    

n=3  —> 18   

n=4 —->30  

 3,9,18,30  -> 3 ( 1, 3, 6,10 )

The standard nth term for 1, 3, 6 …. is (n/2)(n+1)

Hence the nth series for q = (3n/2)(n+1)