Nicholas Rhabdas

First page of Notice sur les deux lettres arithmétiques de Nicolas Rhabdas, published in 1886 in French. Nicholas Artabasdos Rhabdas was an early-14th century Byzantine mathematician. Born in Smyrna, he occupied a position in imperial administration in Constantinople. He is known for three mathematical letters and an unpublished grammatical treatise.

Biography Little is known about his life. Nicholas Artabasdos Rhabdas was born in Smyrna, and occupied a "high-brow imperial functionary of the imperial fiscal administration" position in Constantinople c. 1320–1342. Nicholas Adontz argued, based on his name (from Armenian Artavazd) that he was certainly Armenian and had "just arrived in Smyrna from the east" and was not an old resident of Byzantium.

A. Riehle offered new periodization of Rhabdas' life, and assumed that he was born c. 1295, based on a letter to Andronikos Zarides, that tells that "a partial solar eclipse will occur on June 26, 1321, while a lunar eclipse will take place on July 10, 1321." Manuel Moschopoulos dedicated to Rhabdas a treatise on magic squares,

First one, to Theodore Tzavoukhes of Klazomenai, usually called "Letter to Tzavoukhes", is about arithmetical computation of fractions, square roots of nonsquare numbers, the date of Easter, In the letter Rhabdas calculates the date of Easter for a "current year", that's stated as 1341. Written on November 16, 1322, it contains a "procedure by means of which every arithmetic and geometric means can be found, either being of a double ratio or of a triple or of a multiple or of a multiple-epimoric or of a multiple-epimeric, or epidimeric, and in general of whatever it is of all ratios". The unpublished work was found in a codex in Paris. Acerbi calls this Procedure "a poor piece of mathematics", marred with errors.