Lucas

Returns the desired Lucas number. Similar to the Fibonacci numbers, each Lucas number is defined to be the sum of its two immediately previous terms. The first two Lucas numbers are $L_0=2$, $L_1=1$ and for $n$ greater than 2, $L_n=L_{n-1}+L_{n-2}$.

lucas(Integer)

Description

Given an integer $n$, returns $L_n$.