Arithmetic Sequence of 4 Terms with 3 Distinct Prime Factors

Theorem
The arithmetic progression:
 * $30, 66, 102, 138$

is the smallesr of $4$ terms which consists entirely of positive integers each with $3$ distinct prime factors.

Proof
We demonstrate that this is indeed an arithmetic progression:

demonstrating the common difference of $36$.

Then we note:

It remains to be shown that it is the smallest such arithmetic progression.