John Riordan (1903–1988; Bell Labs, 1926–1968). Distinguished Bell Labs mathematician, author of classic books on combinatorics.
See the Wikipedia article about him for more information.
The following quotation is an extract from an interview with me that appeared in the IEEE Information Theory Society Newsletter, volume 47 (number 4), December 1997, pages 3-4, 35-37.
At the end of my first year as a graduate student at Cornell, in 1962, I managed to arrange a summer job at Bell Labs in Holmdel. ... During that summer I met another of my heroes, John Riordan, one of the great early workers in combinatorics. His book An Introduction to Combinatorial Analysis is a classic. He was working at Bell Labs in West Street in Manhattan at that time. One of my earliest papers, on a problem that came up in my thesis work, was a joint paper with him. [The enumeration of rooted trees by total height, J. Australian Math. Soc. 10 (1969), 278-282; see sequence A000435]
N. J. A. Sloane, Nov 15 2010