The quantity of sts is multiple 6 + 3.
1st row and every odd row: knit;
2nd row: knit;
4th and 6th rows: 3 purls, * 3 knit sts, 3 purls*; repeat from * to *;
8th and 10th rows: knit;
12th and 14th rows: 3 knit sts, * 3 purls, 3 knit sts*; repeat from * to *;
16th row: knit.
Repeat 1st-16th rows.