Divisor-sum convolution identity of weights four and eight
= Divisor-sum convolution identity of weights four and eight
The identity $E_8=E_4^2$ gives
$$
\sigma_7(n)=\sigma_3(n)+120\sum_{i=1}^{n-1}\sigma_3(i)\sigma_3(n-i).
$$
= Divisor-sum convolution identity of weights four and eight
The identity $E_8=E_4^2$ gives
$$
\sigma_7(n)=\sigma_3(n)+120\sum_{i=1}^{n-1}\sigma_3(i)\sigma_3(n-i).
$$