CO 45, longtail
Row 1: K1, *k2, p1; rep from * to end to last 2 sts, k2
Row 2: K1, p1, *k2, p1; rep from * to end to last st, k1
Rep rows 1-2 until you have reached the desired length. BO using JSSBO or another stretchy one. Fasten off, and weave in any remaining tails.
My finished scarf is 10"x62". This stitch is reversible, which is nice. Sometimes I don't like knit scares that aren't reversible, since then you can see the wrong side.