# Tutorial by Topics: number

## Fibonacci Number

Fibonacci Numbers is the integer sequence (OEIS A000045) F(n) that obeys the following recurrence:

`F(n) = F(n-1) + F(n-2)`

For F(0) = 0, F(1) = 1, the series thus formed is 0, 1, 1, 2, 3, 5, 8, 13, 21, ...

Fibonacci numbers appear in several areas of Discrete Mathematics and Algorithms.

## Random Number Generation

Rust has a built in capability to provide random number generation through the rand crate. Once part of the Rust standard library, the functionality of the rand crate was separated to allow its development to stabilize separate to the rest of the Rust project. This topic will cover how to simply add the rand crate, then generate and output a random number in Rust.

## Working with numbers

Progress ABL supports three number formats: 32 and 64 bit integers and floats.

## Outputting numbers

Ada's standard packages provide for output of all numeric types. The format of output can be adjusted in many ways.

## Formatting phone numbers with pattern.

This example show you how to format phone numbers with a patter