Divisor Sum of 343

Example of Sigma Function of Power of Prime

 * $\map \sigma {343} = 400$

where $\sigma$ denotes the $\sigma$ function.

Proof
From Sigma Function of Power of Prime:
 * $\map \sigma {p^k} = \dfrac {p^{k + 1} - 1} {p_i - 1}$

We have that:
 * $343 = 7^3$

Hence:

Thus we have that:
 * $7^0 + 7^2 + 7^2 + 7^3 = 20^2$