LCM( 1, 4 ) = 4
The formula for finding LCM is
$$ \text{LCM} (a, b) = \frac{ a \cdot b }{ \text{GCD}(a,b)} $$In this example we have: a = 1, b = 4 and GCD(1, 4) = 1.
$$ \text{LCM} (1, 4) = \frac{ 1 \cdot 4 }{ \text{GCD}(1,4)} = \frac{ 4 }{ 1 } = 4 $$