riddle of the week

This article is originally published at https://xianblog.wordpress.com

The Riddler of April 1 offered this simple question:

start with the number 1 and then try to reach a target number through a series of steps. For each step, you can always choose to double the number you currently have. However, if the number happens to be one (1) more than an odd multiple of 3, you can choose to “reduce” — that is, subtract 1 and then divide by 3. What is the smallest positive integer one cannot reach this way?

Which I turned into R steps (while waiting for flight AF19 to Paris)

  while((!(x-1)%%3)&((x-1)%%6)){
    oor[2*x]TRUE
    oor[x<-(x-1)%/%3]=TRUE}

but running an exhaustive search till 10⁸ did not spot any missing integer… Maybe an April fool joke (as the quick riddle was asking for the simplest representation of (x-a)(x-b)…(x-z)…!)

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This article is originally published at https://xianblog.wordpress.com
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