I just bought one at a thrift store because I like the color and the pattern and I may use the pattern later. Here's my deconstruction of it....
I think it's a multiple of 13 sts plus 12 to CO.
Knit garter for 4 rows, k3, purl across, k3 on the next row (WS).
K3, k2, p2, k2, yo, k2, p3tog, k2, yo repeat across, end with k2, p2, k2, k3. Purl all WS rows with k3 on both ends for a garter border. End with k4 rows, BO.