with , where is the floor function.
The first few values for ,
1, 2, ... are 1, 3, 3, 4, 7, 7, 7, 9, 9, 10, 13, ... (OEIS A007448).
Conway and Guy (1996, p. 15) note that is the alphabetically first prime
number in the American system of large number terminology, and term this "Knuth's
number."