183 (number)

183 is a perfect totient number, a number that is equal to the sum of its iterated totients.^[1]

Because ${\displaystyle 183=13^{2}+13+1}$, it is the number of points in a projective plane over the finite field ${\displaystyle \mathbb {Z} _{13}}$.^[2] It is a repdigit in tredecimal (111₁₃). 183 is the fourth element of a divisibility sequence ${\displaystyle 1,3,13,183,\dots }$ in which the ${\displaystyle n}$th number ${\displaystyle a_{n}}$ can be computed as $${\displaystyle a_{n}=a_{n-1}^{2}+a_{n-1}+1={\bigl \lfloor }x^{2^{n}}{\bigr \rfloor },}$$ for a transcendental number ${\displaystyle x\approx 1.38509}$.^[3][4] This sequence counts the number of trees of height ${\displaystyle \leq n}$ in which each node can have at most two children.^[3][5]

There are 183 different semiorders on four labeled elements.^[6]

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