Percy Alexander MacMahon (26 September 1854 – 25 December 1929) was an English mathematician, especially noted in connection with the partitions of numbers and enumerative combinatorics.

At the age of 14 he won a Junior Scholarship to Cheltenham College, which he attended as a day boy from 10 February 1868 until December 1870.

In early 1878 MacMahon returned to England and the sequence of events began which led to him becoming a mathematician rather than a soldier.

Successful completion of the course resulted in the award of the letters "p.a.c" (passed advanced class) after MacMahon's name in the Army List.

After he passed the Advanced Course and had been promoted to the rank of captain on 29 October 1881, MacMahon took up a post as instructor at the Royal Military Academy on 23 March 1882.

Joseph Larmor, in a letter to The Times published after MacMahon's death, wrote, 'The young Captain threw himself with indomitable zeal and insight into the great problems of the rising edifice of algebraic forms, as was being developed by Cayley, Sylvester and Salmon.’ In 1891 MacMahon took up a new post as military instructor in electricity at the Royal Artillery College, Woolwich.

[6] A reviewer in "Science Progress in the Twentieth Century", writes: Richard P. Stanley considers MacMahon as the most influential mathematician in enumerative combinatorics pre-1960.

[9] Gian-Carlo Rota notes in his introduction to Volume I of MacMahon's Collected Papers: It would have been fascinating to be present at one of the battles of arithmetical wits at Trinity College, when MacMahon would regularly trounce Ramanujan by the display of superior ability for fast mental calculation (as reported by D. C. Spencer, who heard it from G. H. Hardy).

The copyright holder has licensed the content in a manner that permits reuse under CC BY-SA 3.0 and GFDL.