| public static pellNumber ( integer $n ) : array | ||
| $n | integer | How many numbers in the sequence |
| Результат | array | Indexed from 0 |
public static function pellNumber(int $n) : array
{
$pell = [];
// Bad input; return empty list
if ($n <= 0) {
return $pell;
}
// Base case (n = 1): P₀ = 0
$pell[] = 0;
if ($n === 1) {
return $pell;
}
// Base case (n = 2): P₀ = 0, P₁ = 1
$pell[] = 1;
if ($n === 2) {
return $pell;
}
// Standard iterative case: Pᵢ = 2Pᵢ₋₁ + Pᵢ₋₂
for ($i = 2; $i < $n; $i++) {
$pell[$i] = 2 * $pell[$i - 1] + $pell[$i - 2];
}
return $pell;
}