1*0^2 + 2*0^2 + 3*0^2 + 4*4^2 = 64.
1*0^2 + 2*0^2 + 3*4^2 + 4*2^2 = 64.
1*1^2 + 2*0^2 + 3*3^2 + 4*3^2 = 64.
1*1^2 + 2*4^2 + 3*3^2 + 4*1^2 = 64.
1*2^2 + 2*2^2 + 3*4^2 + 4*1^2 = 64.
1*2^2 + 2*4^2 + 3*2^2 + 4*2^2 = 64.
1*4^2 + 2*0^2 + 3*2^2 + 4*3^2 = 64.
1*4^2 + 2*0^2 + 3*4^2 + 4*0^2 = 64.
1*4^2 + 2*4^2 + 3*0^2 + 4*2^2 = 64.
1*4^2 + 2*4^2 + 3*2^2 + 4*1^2 = 64.
1*5^2 + 2*0^2 + 3*1^2 + 4*3^2 = 64.
1*5^2 + 2*2^2 + 3*3^2 + 4*1^2 = 64.
1*5^2 + 2*4^2 + 3*1^2 + 4*1^2 = 64.
1*6^2 + 2*0^2 + 3*2^2 + 4*2^2 = 64.
1*7^2 + 2*2^2 + 3*1^2 + 4*1^2 = 64.
1*8^2 + 2*0^2 + 3*0^2 + 4*0^2 = 64.
So a(4) = 16.
|