1 + 3 + 5 + 7 + ___ = ?
1 => x 3 => 0x xx 5 => 00x 00x xxx 7 => 000x 000x 000x xxxx 9 => 0000x 0000x 0000x 0000x xxxxx
1 + 3 + 5 + .... + ___ = ? (數列有 90 個)
37 + 39 + 41 + 43 + .... + ___ = ? (數列有 90 個)