3^2 - 1 = 8 9^2 - 3 = 78 18^2 - 6 = 318 27^2 - 9 = 720 36^2 - 12 = 1284 45^2 - 15 = 2010

therefore answer is 1284

8 = (3*1)^2-1 78 = (3*3)^2-3 318 = (3*6)^2-6 720 = (3*9)^2-9 1284 = (3*12)^2-12 2010 = (3*15)^2-15

Answer is 1284

What is the next number of the following series: 8, 78, 318, 720, ? Also tell the relation between 8,78