(define sum-of-squares (make-general-series + square))
     (sum-of-squares 5) ⇒ 55 (1 + 4 + 9 + 16 + 25)
     
     (define sum-of-cubes (make-general-series + cube))
     (sum-of-cubes 5) ⇒ 225 (1 + 8 + 27 + 64 + 125)
     
     (define product-of-cubes (make-general-series * cube))
     (product-of-cubes 5) ⇒ 1728000 (1 * 8 * 27 * 64 * 125)