An autogram ( = self, = letter) is a sentence that describes itself in the sense of providing an inventory of its own characters. They were invented by Lee Sallows, who also coined the word autogram. An essential feature is the use of full cardinal number names such as "one", "two", etc., in recording character counts. Autograms are also called 'self-enumerating' or 'self-documenting' sentences. Often, letter counts only are recorded while punctuation signs are ignored, as in this example: The first autogram to be published was composed by Sallows in 1982 and appeared in Douglas Hofstadter's "Metamagical Themas" column in Scientific American. The task of producing an autogram is perplexing because the object to be described cannot be known until its description is first complete. Self-enumerating pangrams A type of autogram that has attracted special interest is the autogramic pangram, a self-enumerating sentence in which every letter of the alphabet occurs at least once. Certain letters do not appear in either of the two autograms above, which are therefore not pangrams. The first ever self-enumerating pangram appeared in a Dutch newspaper and was composed by Rudy Kousbroek. Sallows, who lives in the Netherlands, was challenged by Kousbroek to produce a self-enumerating 'translation' of this pangram into English—an impossible-seeming task. This prompted Sallows to construct an electronic Pangram Machine. Eventually the machine succeeded, producing the example below which was published in Scientific American in October 1984: Sallows wondered if one could produce a pangram that counts its letters as percentages of the whole sentence–a particularly difficult task since such percentages usually won't be exact integers. He mentioned the problem to Chris Patuzzo and in late 2015 Patuzzo produced the following solution: Later in 2017, Matthias Belz decided to push the boundaries further by making a pangrammatic autogram with a precision of five decimal places: However, no matter the precision of the rounding, the percentage of the letters used are still not exact. Therefore, in that same year Matthias Belz went on to create an pangrammatic autogram that uses exact percentages instead of rounded values: A shorter exact percentage autogram can be formed if the pangrammatic property is elided: Generalizations Autograms exist that exhibit extra self-descriptive features. Besides counting each letter, here the total number of letters appearing is also named: Just as an autogram is a sentence that describes itself, so there exist closed chains of sentences each of which describes