Cast on 14. (Cast on whatever amount that when divided by two, and added together, equals an amount divisible by 3. For example, 14/2=7. 14+7=21. 21/3 =7)

YO=Yarn Over
Slp pw=Slip purl wise.
K1=Knit 1.
K2TOG=Knit 2 together.

Row 1. YO, Slp pw, k1.
Row 2. (And every row after) YO, Slp pw, k2tog.

Tip. The stitch you are meant to slip purl wise will always be the stitch you k2tog on the prior row - except for the first time when you knit row 2. The stitch you will be slipping purl wise will be the stitch you knit prior.