Ludium - Learn by Doing

Lucas Numbers by Recursion

The Lucas numbers are built the same way as the Fibonacci numbers but start from different values: L(1) = 1, L(2) = 3, and every later term is the sum of the two terms immediately before it.

Assume you are given an integer n that is at least 1. Write the function lucas(n) that returns the nth Lucas number. Write it recursively.

lucas(1) -> 1
lucas(2) -> 3
lucas(3) -> 4
lucas(6) -> 18

def lucas(n):
    """Return the nth Lucas number. n is an int >= 1."""
    pass

def lucas(n):
    """Return the nth Lucas number. n is an int >= 1."""
    pass

Scratchpad— run any Python to test ideas

# Scratchpad — run any Python here to test ideas.
# Anything you write below stays separate from the problem's tests.

print("hello, world")

# Scratchpad — run any Python here to test ideas.
# Anything you write below stays separate from the problem's tests.

print("hello, world")

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Visible tests · 2Examples — click to expand

The first two terms are 1 and 3

lucas(6) is 18

Hidden tests · 3Bodies hidden — pass/fail only

Hidden test 1

Hidden test 2

Hidden test 3

Coding challenges on recursion on numbers and lists

Lucas Numbers by Recursion

Coding challenges on recursion on numbers and lists

Lucas Numbers by Recursion