# Lucas
> Compute the nth [Lucas number][lucas-number].
The [Lucas numbers][lucas-number] are the integer sequence
The sequence is defined by the recurrence relation
## Usage
```javascript
var lucas = require( '@stdlib/math/base/special/lucas' );
```
#### lucas( n )
Computes the nth [Lucas number][lucas-number].
```javascript
var v = lucas( 0 );
// returns 2
v = lucas( 1 );
// returns 1
v = lucas( 2 );
// returns 3
v = lucas( 3 );
// returns 4
v = lucas( 76 );
// returns 7639424778862807
```
If `n > 76`, the function returns `NaN`, as larger [Lucas numbers][lucas-number] cannot be safely represented in [double-precision floating-point format][ieee754].
```javascript
var v = lucas( 77 );
// returns NaN
```
If not provided a nonnegative integer value, the function returns `NaN`.
```javascript
var v = lucas( 3.14 );
// returns NaN
v = lucas( -1 );
// returns NaN
```
If provided `NaN`, the function returns `NaN`.
```javascript
var v = lucas( NaN );
// returns NaN
```
## Examples
```javascript
var lucas = require( '@stdlib/math/base/special/lucas' );
var v;
var i;
for ( i = 0; i < 77; i++ ) {
v = lucas( i );
console.log( v );
}
```
[lucas-number]: https://en.wikipedia.org/wiki/Lucas_number
[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
