Arithmetic Sequence of 4 Terms with 3 Distinct Prime Factors

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

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

Proof
We demonstrate that this is indeed an arithmetic sequence:

demonstrating the common difference of $36$.

Then we note:

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