; a median-of-three killer sequence (define (m3-killer n) (if (odd? n) (error 'm3-killer "length must be even") (let* ((k (/ n 2)) (ary (make-vector n #f))) (do ((i 1 (+ i 1))) ((< k i) ary) (when (odd? i) (vector-set! ary (- i 1) i) (vector-set! ary i (+ k i))) (vector-set! ary (+ k i -1) (+ i i)))))) (display (m3-killer 20)) (newline)