; 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)
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