## σ(a) = σ(b) = a + b + 1

To find pairs   $(a, b)$,   $a < b$   such that   $\sigma(a) = \sigma(b) = a + b + 1$

for example,

$\sigma(48) \; = \; \sigma(75) \; = \; 48 \; + \; 75 \; + \; 1 \; = \; 124$

$\sigma(140) \; = \; \sigma(195) \; = \; 140 \; + \; 195 \; + \; 1 \; = \; 336$

$\sigma(1575) \; = \; \sigma(1648) \; = \; 1575 \; + \; 1648 \; + \; 1 \; = \; 3224$

$\sigma(1050) \; = \; \sigma(1925) \; = \; 1050 \; + \; 1925 \; + \; 1 \; = \; 2976$

$\sigma(2024) \; = \; \sigma(2295) \; = \; 2024 \; + \; 2295 \; + \; 1 \; = \; 4320$

Find other pairs