John Kersey the elder

John Kersey the elder was an English mathematician and textbook writer who lived from 1616 to 1677, baptised at Bodicote near Banbury in Oxfordshire on 23 November 1616. He came to London and made his living as a teacher, gaining a wide reputation as a teacher of mathematics, and was for a time tutor to the sons of Sir Alexander Denton of Hillesden House. John Collins persuaded him to write his work on algebra, and he edited the second edition of Edmund Wingate's Arithmetic in 1650 and later issues until 1683. His first and principal original work, The Elements of that Mathematical Art, commonly called Algebra, appeared in two folio volumes in 1673 and 1674 and became a standard authority, praised by John Wallis and Collins and later by Charles Hutton. It contains the earliest known reference to the aliquot formula for the number of divisors of a positive integer.