(DEFPROP DELTA (LAMBDA (K N)
                         (DIFFERENCE (*TIMES K (QUOTIENT PI2
                                                         (SUB1 N)))
                                     PI4))
           EXPR)
  (DEFPROP DELTALIST (LAMBDA (N)
                             (FOR NEW K := (0 (SUB1 N))
                                  XLIST
                                  (DELTAPR K N)))
           EXPR)
  (DEFPROP DELTAPR (LAMBDA (K N)
                           (PROG (X)
                                 (SETQ X (DELTA K N))
                                 (RETURN (CONS (COS X)
                                               (SIN X)))))
           EXPR)
STOP