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Landau's function
Landau's function g(n) is defined for every natural number n to be the largest order of an element of the symmetric group Sn. Equivalently, g(n) is the largest least common multiple of any partition of n.
For instance, 5 = 2 + 3 and lcm(2,3) = 6. No other partition of 5 yields a bigger lcm, so g(5) = 6. An element of order 6 in the group S5 can be written in cycle notation as (1 2) (3 4 5).
The integer sequence g(0) = 1, g(1) = 1, g(2) = 2, g(3) = 3, g(4) = 4, g(5) = 6, g(6) = 6, g(7) = 12, g(8) = 15, ... is A000793.
The sequence is named after Edmund Landau, who proved that
(where ln denotes the natural logarithm).
The following recursive formula can be used to compute g(n):
External links
On-Line Encyclopedia of Integer Sequences: Sequence A000793, Landau's function on the natural numbers.
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