Multiple of 2
Abbreviations: C: colour; p: purl; k: knit; yfwd: yarn forward; sl: slip; ybk: yarn back; rep: repeat;
Terms: yarn forward: bring the yarn forward (towards you); slip1: slip the next stitch instead of knitting it; yarn back: put the yarn to the back (away from you)
Row 1: C1: p
Row 2: C2: *k1, yfwd, sl 1 purlwise, ybk*, rep from * to * until end
Row 3: C2: p
Row 4: C1: k1, *k 1, yfwd, sl 1 purlwise, ybk*, rep from * to * until last st, k1
These 4 rows form the pattern.