import java.util.*;

/** An immutable List<Double> representing the sequence ax^2 + bx + c */
public class QuadraticSequence extends AbstractList<Double> {
    final int size;
    final double a, b, c;

    QuadraticSequence(double a, double b, double c, int size) {
        this.a = a; this.b = b; this.c = c; this.size = size;
    }

    @Override public int size() { return size; }

    @Override public Double get(int index) {
        if (index<0 || index>=size) throw new ArrayIndexOutOfBoundsException();
        return a*index*index + b*index + c;
    }
}