Square Numbers whose Divisor Sum is Square/Examples/20

Example of Square Number whose Divisor Sum is Square

$\map {\sigma_1} {20^2} = 31^2$

Proof

We have that $20^2 = 400$.

Then from $\sigma_1$ of $400$:

$\map {\sigma_1} {400} = 961$

which equals $31^2$.

$\blacksquare$

Sources

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $81$