Spelling ①: 1× 6, for example, "123456" is "65432 1" after rotating 180 degrees, and "123456" after rotating 180 degrees. In fact, "123456" (reverse reading is "65432 1") rotates 1 degree, 2 degrees, ..., 359 degrees, and the relative position is always "123456" or "65432/kloc". So divide by two.

Spelling ②: 2× 3, which is the same after rotating 180 degrees, is regarded as spelling. So divide by two.

The 6× 1 formula and the 3×2 formula are actually obtained by rotating the above spelling forward/backward by 90 degrees, so they are no longer considered.