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Old 2018-11-08, 23:09   #9
retina
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"The unspeakable one"
Jun 2006
My evil lair

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Quote:
Originally Posted by Brian-E View Post
I'm wondering what "Captcha" techniques are so effective here. I remember there is that question "what is 2^32-1?" (or something along those lines).
Well, let's see ...

https://mersenneforum.org/register.php?do=register
  1. Please enter the six letters or digits that appear in the image opposite.
  2. What is 2^32-1 in decimal notation?
  3. What year did Bernard Hinault win his first Vuelta a EspaƱa?
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