Pythagorean pattern is reversible and would also make a great design for a coordinating afghan/blanket. Looks the same on both sides.
Cast on a multiple of 12 stitches.
Rows 1 - 2: * Purl 6, knit 6; repeat from * to end.
Rows 3 - 4: * Knit 1, purl 5, knit 5, purl 1; repeat from * to end.
Rows 5 - 6: * Knit 2, purl 4, knit 4, purl 2; repeat from * to end.
Rows 7 - 8: * Knit 3, purl 3; repeat from * to end.
Rows 9 - 10: * Knit 4, purl 2, knit 2, purl 4; repeat from * to end.
Rows 11 - 12: * Knit 5, purl 1, knit 1, purl 5; repeat from * to end.
Rows 13 - 14: * Knit 6, purl 6; repeat from * to end.
Rows 15 - 16: * Purl 6, knit 6; repeat from * to end.
Rows 17 - 18: * Purl 5, knit 1, purl 1, knit 5; repeat from * to end.
Rows 19 - 20: * Purl 4, knit 2, purl 2, knit 4; repeat from * to end.
Rows 21 - 22: * Purl 3, knit 3; repeat from * to end.
Rows 23 - 24: * Purl 2, knit 4, purl 4, knit 2; repeat from * to end.
Rows 25 - 26: * Purl 1, knit 5, purl 5, knit 1; repeat from * to end.
Rows 27 - 28: * Knit 6, purl 6; repeat from * to end.
Repeat Rows 1 - 28

Pythagorean stitch in the round