He was a founder of the Jewish Mathematicians' Association, Mathesis Artium Genetrix, and published a number of works on Hebrew grammar and mathematics.

[1] Born in Naarden, Lemans was educated by his father and (in mathematics) by Judah Littwack.

He helped found Hanokh la na'ar al pi darkho, a society for reform in Jewish education, for which he published a number of Hebrew textbooks.

In 1808 he published Ma'amar Imrah Ẓerufah (Article on Pure Speech), in which he advocated for the abandonment of Ashkenazi pronunciation of Hebrew in favour of the Sephardi one,[2] and some years later a Hebrew grammar, Rudimenta (1820).

In collaboration with Samuel Israel Mulder he published a Hebrew-Dutch dictionary in 1829-1831.