37. By symmetry, we may assume a⩾b⩾c. Note that when (a,b,c)=(2,2,2),(3,2,2),(3,3,2),(4,2,2), the value of the given algebraic expression A is 2,23,817,411, respectively. This indicates that when a+b+c⩽8, A⩾23.
Next, we prove that when a+b+c⩾9, we have A⩾23.
In fact,
A⩾23⇔(a+b+c)2−2([a,b]+[b,c]+[c,a])⩾3(a+b+c)⇔a2+b2+c2+2∑(ab−[a,b])⩾3(a+b+c)
Since for positive integers x,y, we have xy⩾[x,y], it suffices to prove:
a2+b2+c2⩾3(a+b+c)
Given a+b+c⩾9, to prove (1) holds, it suffices to prove:
⇔⇔⇔a2+b2+c2⩾31(a+b+c)23(a2+b2+c2)⩾(a+b+c)22(a2+b2+c2)−2(ab+bc+ca)⩾0(a−b)2+(b−c)2+(c−a)2⩾0
The last inequality is obviously true.
Therefore, the minimum value of the given algebraic expression is 23.