Yeah, that works. I tried it. With 21 to start:
*(K1,P1,K1) into next stitch, K2tog, K1, K2tog, (K1, P1, K1) into next stitch, repeat from * to end.
*Into the first stitch on the LH (left hand) needle, knit it but don't take it off, move the yarn to the front, purl it, don't take it off, move the yarn to the back again and knit it one more time, now let the stitch off the LH needle, you have 3 new stitch loops on the RH (right hand) needle. K2tog, k1, k2tog, do the 3 in one again. Repeat across from the * and you'll have 27 when you're done.
You make 21 into 27 because you make 1 into 3 (+2 each time), 6 times for 12 stitches increased, and you k2tog (-1 each time) 6 times for a total of 6 stitches decreased. 21+12=33-6=27 :lol: