Answer: 312211 John Conway's "look and say" sequence has no digits other than 1, 2, and 3 in it, unless the seed number contains such a digit or a run of more than three of the same digit. A degenerate sequence appears with the seed of 22.
Answer: O- People with O- blood can give blood to anyone. The other blood types can only donate to certain people depending on their blood type. For example, if you are AB+ you can only donate to other AB+ blood types, but you can receive blood from anyone.
Answer: Paul Erdős, of course! As the Erdős number describes the "collaborative distance" in authorship of mathematical papers between mathematician Paul Erdős and another person it is only natural that Paul Erdős holds this position.
