def layer_rows(layer):
	"""
	Given a layer return each row as a list.
	"""

	els = range((2*(layer-1)-1)*(2*(layer-1)-1) + 1, (2*layer-1)*(2*layer-1) + 1)

	side_length = len(els) / 4

	return [els[:side_length], els[side_length:2*side_length], els[2*side_length:3*side_length], els[3*side_length:]]