“"Arithmetic Introduction" is the most complete exposition extant of Pythagorean arithmetic. It deals in great part with the same subjects as the arithmetical books of Euclid's "Elements," but where Euclid represents numbers by straight lines, Nicomachus uses arithmetical notation with ordinary language when undetermined numbers are expressed. His treatment of {{w|polygonal number}}s and {{w|pyramidal number}}s was of influence on medieval arithmetic, especially through Boetius.”