probability

Coin Flipping Problem

Elo from LessWrong suggested this problem:

I write a sequence of n heads or tails on paper.

I then start flipping a sequence of n coins. If next coin does not match my sequence, I restart a new sequence of n coins.

What is the rule for the relationship between how many coins I need to flip to get the sequence I have pre-committed to and the length of the sequence of?

Discussion there:

http://lesswrong.com/r/discussion/lw/pg3/open_thread_september_25_october_1_2017/dxlt

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games

Prime Crossword

3,7

1,1

37 and 11 are primes. As 31 and 71.

Can you produce a bigger one than 2×2? 5×5 perhaps, or even larger “prime crossword”? In decimal, binary, hexadecimal or whatever notation.

You might discuss it here:

http://lesswrong.com/r/discussion/lw/pf6/open_thread_september_18_september_24_2017/dxcr

 

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