Find a8 and a15 whose nth term is

Find a8 and a15 whose nth term is
Solution :
In a8, 8 is even in a15, 15 is odd 
an  = (n2 - 1)/(n + 3)
a8  = (82 - 1)/(8 + 3)
  =  (64 - 1)/11
  =  63/11
an  = n2/(2n + 1)
a15  = 152/(2(15) + 1)
  =  225/(30 + 1)
  =  225/31