"Two times ten is twenty, eleven twice is twenty-two, Double twelve that's twenty-four, thirteen twice is twenty-six, Fourteen twice is twenty-eight, fifteen twice is thirty, now you're buildin' up on thirty: Sixteen twice is thirty-two, elementary. Seventeen twice is thirty-four, elementary. Eighteen twice is thirty-six, elementary. Nineteen twice is thirty-eight, elementary. Twenty twice is forty, and it must occur to you, You can double any number, all you do is multiply by two..."