$$(a+b+c)^{3}-a^{3}-b^{3}-c^{3}$$
$3\left(a+b\right)\left(a+c\right)\left(b+c\right)$
$3ab^{2}+6abc+3ac^{2}+3ba^{2}+3bc^{2}+3ca^{2}+3cb^{2}$
