Answer
16, 41, 66, 91, 116, 141, 166, 191, 216, 241, 266, 291, 316, 341, 366, 391, 416, 441, 466, 491
Work Step by Step
He obtained the number 16, so the 16th client is the first one sampled. Then, every 25th client after that person is sampled:
$16$
$16+25=41$
$41+25=66$
$66+25=91$
$91+25=116$
$116+25=141$
$141+25=166$
$166+25=191$
$191+25=216$
$216+25=241$
$241+25=266$
$266+25=291$
$291+25=316$
$316+25=341$
$341+25=366$
$366+25=391$
$391+25=416$
$416+25=441$
$441+25=466$
$466+25=491$
