Here's my whack at it... definitely not a mathematician, but I figured I'd try.
Cast on 78 sts, place marker.
Work 11" in K2 P2 ribbing.
Work 1 round in K2tog P2tog instead of K2 P2.
Work 5 rounds of P1 K1 ribbing.
Work 1 row of K2tog.
Knit 1 row.
Work another row of K2tog.
Break off yarn, draw through remaining 10 sts, fasten securely.
If I've omitted any important details that would make the final project look weird, someone who actually knows what they're doing can correct me.