16 = 4*2^2
36 = 4*3^2
64 = 4*4^2
100 = 4*5^2
144 = 4*6^2
-(No.100)...4 * 100 power 2 = 40000
5 = 2 + 3
10 = 5 + 5
17 = 10 + 7
26 = 17 + 9 .............a(n) = a(n- 1) + (2n- 1)
a( 1) = 2
a(2) = 2 + (2*2 - 1)
a(3)= 2+(2 * 2- 1)+(2 * 3- 1)
a(4)= 2+(2 * 2- 1)+(2 * 3- 1)+(2 * 4- 1)
....
a(50) = 2 + 2*(2 + 3 + 4 +)....+ 50) - (50 - 1)
= 2*( 1 + 2 + 3 + ....+ 50) - 50 + 1
= 2*[( 1 + 50)*50/2] - 50 + 1
= 50*5 1 - 50 + 1
= 50*50 + 1
= 250 1