(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)