## Fibonacci Numbers Calculator

## Answers to Questions

### How to calculate the Fibonacci sequence?

Numbers from the **Fibonacci sequence** are equal to the addition of the 2 previous terms, they follow the recurrence formula: $$ F(n+2) = F(n) + F(n+1) $$

To initiate the sequence, by default, the two first terms are $ F(0) = 0 $ and $ F(1) = 1 $

Example: F2 = F0+F1 = 0+1 = 1

F3 = F1+F2 = 1+1 = 2

F10 = F8+F9, etc.

### What are the first terms of the Fibonacci sequence?

**Fibonacci numbers** are:

F(0)= | 0 |
---|---|

F(1)= | 1 |

F(2)= | 1 |

F(3)= | 2 |

F(4)= | 3 |

F(5)= | 5 |

F(6)= | 8 |

F(7)= | 13 |

F(8)= | 21 |

F(9)= | 34 |

F(10)= | 55 |

For the next Fibonacci terms, use the calculator above.

### How to compute the previous Fibonacci term?

Each term in the sequence is equal to the previous multiplied by approximately $ \varphi = 1.618 $ (golden number).

Example: $ F(10) = 55 $, $ 55/\varphi \approx 33.99 $ and in fact $ F(9) = 34 $

### What is the Fibonacci Rabbits' problem?

The rabbits' problem is a problem proposed by Leonardo Fibonacci in 1200.

There is a rabbit couple (male + female) and every month a couple breeds and give birth to a new pair of rabbits which in turn can reproduce itself after 2 months. How many rabbits will be born after X months?

In the beginning there is 1 couple then

1 month | 1 couple |

two months | 2 couples |

three months | 3 couples |

4 months | 5 couples |

5 months | 8 couples |

6 months | 13 couples |

7 months | 21 couples |

8 months | 34 couples |

Each month, the total number of rabbits is equal to the sum of the numbers of the previous two months because it is the number of existing rabbits (the previous month) plus the number of babies born from rabbits couples who have at least two months (hence the number of rabbits 2 months ago). The numbers found are the numbers of the **Fibonacci sequence**.

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