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- Fibonacci function or sequence 239 answers
Background of Lucas Numbers
The French mathematician, Edouard Lucas (1842-1891), who gave the name to the Fibonacci Numbers, found a similar series occurs often when he was investigating Fibonacci number patterns.
The Fibonacci rule of adding the latest two to get the next is kept, but here we start from 2 and 1 (in this order) instead of 0 and 1 for the (ordinary) Fibonacci numbers. The series, called the Lucas Numbers after him, is defined as follows: where we write its members as Ln, for Lucas:
0 < x < ∞
The input will be a positive integer starting at 0.
The output must be a positive integer.
What to do?
Add the Fibonacci numbers to the Lucas numbers.
You will input the index.
The output will be the addition of the Lucas and Fibonacci numbers.
F(0) = 0,
F(1) = 1,
F(n) = F(n-1) + F(n-2)
L(0) = 2,
L(1) = 1,
L(n) = L(n-1) + L(n-2)
Standard Code-Golf rules apply, so the shortest answer in bytes wins.
A(0) = 2
A(1) = 2
A(5) = 16
A(10) = 178
A(19) = 13,530
A(25) = 242,786